Glossary for Doors Frames and Hardware

Glossary: Doors, Frames, Hardware & More

Does door and hardware jargon have you confused? Brush up on your knowledge or learn more about a term with our glossary.

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AAADM – American Association of Automatic Door Manufacturers, a trade association of power-operated automatic door manufacturers.

Active Door / Active Leaf (in a pair of doors) – The leaf that opens first and the one to which the main operating hardware (i.e. lock/latch) is applied.

Actual Door Size – The largest measured width by height of the actual door leaf. This is equal to the nominal door size minus clearances to assure the door fits into the opening. Also referred to as Net Door Size.

ADA – Americans with Disabilities Act, signed into law in 1990, is the comprehensive piece of civil rights legislation which prohibits discrimination and guarantees that people with disabilities have the same opportunities as everyone else to participate in mainstream American life.

ADAAG – Americans with Disabilities Act Accessibility Guidelines outline the design requirements for the construction and alteration of facilities. These enforceable standards apply to places of public accommodation, commercial facilities, and state and local government facilities.

Adjustable Frame – A frame with a profile in two or more pieces to accommodate various wall thicknesses. Also referred to as an expandable frame or a split frame.  View Image

Agrifiber Core – A composite wood door core made from the agricultural waste products. Examples of agrifibers include straw particleboard, rice straw, sunflower husk, wheat, etc.

AHC – Architectural Hardware Consultant. This credential indicates that person is trained to recognize builder’s hardware requirements for door openings of all types of public, commercial, industrial and institutional buildings. AHC’s ensure door openings are in compliance with fire, life safety, accessibility, and building code requirements. This credential is earned through the Door and Hardware Institute.

AHJ – Authority Having Jurisdiction. An organization, office, or individual responsible for enforcing the requirements of a code or standard; or for approving equipment, materials, installation, or a procedure. Typically, this person is the local building inspector, official, or fire marshal. This person has the authority to follow or overrule any national standards or codes.

Anchor (of a frame) – The means by which the frame is attached to the surrounding structure.

Anodize – A non-corrosive oxide film placed on the surface of metal by an electrolytic process.

ANSI – American National Standards Institute is the administrator and coordinator of the U.S. private sector voluntary standardization system.

Architectural Hardware – Also referred to as Finish Hardware or Builders Hardware. This is the term applied to all hardware that is used in connection with doors, windows, cabinets, and other movable items. These items do not make any part of a building; instead, they support them and make them work. Examples include door handles, hinges, and deadbolts.

Armor Plate – A plate similar to a kick plate or mop plate but covers the door to a greater height. Its purpose is to protect the door face from marring by carts or gurneys. The range in height from the bottom of the door is typically 18” – 48.”

Armored Front – A plate applied to the front of a mortise lock (on the edge of the door). The purpose is to protect cylinder set screws so they cannot be loosened or tampered with unless this plate is removed. Also known as Edge Plate or Scalp Plate.

Astragal – A molding or strip with the purpose of covering or closing the gap between the edges of a pair of doors, the bottom edge of a flush transom panel, or between the top and bottom leaves of a Dutch door. Some types overlap, others meet at the center line of the gap.

Automatic Door Closer – An electronic door closer which opens a door upon approach or by use of an actuator, such as a push button.

Auxiliary Dead Latch – A supplementary latch that, when depressed, deadlocks the main latchbolt so it cannot be pushed in by end pressure. When a door is in the closed position, this deadlatch is depressed against the strike, which activates the deadlocking of the main bolt.

AWI – Architectural Woodwork Institute is a professional trade organization that publishes woodworking standards.


Backbend – The part of the frame profile which extends from the return and is formed parallel to the wall, inside the frame throat. Also referred to as a double return, double backbend, or a drywall return. View Image.

Backcheck (of a door closer) – An optional feature in hydraulic door closers that prevents the door from opening too fast and slamming against the wall or other objects. The opening swing is slowed at a certain degree and controls the speed of the door during the balance of its opening cycle. This feature is not intended to replace an auxiliary stop. 

Backset (of a hinge) – On a door, this is the distance from the push side edge of the door to the edge of the hinge cutout. On a frame, this is the distance from the stop of the frame to the edge of the hinge cutout. View Image.

Backset (of a lock) – The horizontal distance from the faceplate of the lock to the center line of the knob/lever hub, keyhole, or cylinder. It is measured from the wide side of a beveled door. View Image.

Backset (of a strike) – On a frame, this is the distance from the stop of the frame to the edge of the strike cutout. View Image

Ball Bearing Hinge – A hinge that is equipped with ball bearings between the hinge knuckles to reduce friction.

Bank (of doors) – An opening with 2 or more doors in the same frame. If there are only two doors, a mullion separates the door leaves as opposed to a pair of doors where there is no mullion.

Barber Pole – An effect in book matching of veneer leaves which is due to “tight” and “loose” sides of veneers alternating along the face of the door. These veneer leaves may accept stain or reflect light differently, which results in a noticeable color variation when finished. Barber Poling is considered an acceptable color variation and is not considered a defect.

Base (of a frame) – See Sill.

Beveled Edge (of a door) – The angle of the edge of a door in relation to the inside and outside face. The most commonly used bevel is 1/8 inch in 2 inch (or 3 degrees). Beveling a door is what creates a narrow side and a wide side. The narrow side of the door is the side in contact with the stop of the frame when the door is closed (i.e. the push side). View Image

BHMA – Builders Hardware Manufacturers Association is the trade association for manufacturers of commercial builders hardware.

Bifold Doors – Doors hinged together so they can fold against each other as well as against the door jamb. Bifold doors are most commonly classified as either two- or four-door panels.

Bitting – A number that represents a depth of a cut on a pin tumbler type key. The combination of all cuts on the key are represented in a code system using a series of numbers and/or letters.

Book Match – The practice of matching two or more wood veneer surfaces by flipping alternating pieces so they mirror each other, giving the impression of an open book.

Bored Lock – A lock or latch that fits into a drilled or bored opening in a door. Types of bored locks include tubular and cylindrical locks.

Borrowed Lite – An interior frame that includes stationary glazed openings but does not include a door opening.

Bottom Clearance (of a door) – See Floor Clearance.

Box Strike – A strike that also includes a back plate to enclose the bolt opening in the frame. Metal frames usually have a box already built into the strike reinforcement to protect it from mortar or grout.

Builders Hardware – See Architectural Hardware.

Bull-Nosed Edge (of a door) – A door edge that has a radius. View Image

Butt Hinge – A type of hinge designed for mortising into the edge of the door and into the rabbet of a door frame. It is also known as a fully mortised hinge.

Butted Frame – A frame which sits against the wall structure rather than wraps around it. View Image

Bypass Doors – Two or more doors that open by sliding on a track behind/in front of each other in a horizontal direction.


Cam (of a cylinder) – The rotating piece attached to the end of the cylinder plug to engage the locking mechanism of a lock. View Image

Camlift Hinge – A hinge designed to lift a door to a specific height as it is opened to a specific degree of opening. Commonly used on sound rated doors.

Case (of a lock) – The box containing the lock mechanism. Also known as the lock body.

Cased Open Frame – A frame without a stop and soffit. View Image

Casing – The framing around a door or window.

CDC – Certified Door Consultant. This credential indicates that person is trained in the construction and application of standard and custom hollow metal doors and frames, architectural flush and stile and rail wood doors and aluminum doors and frames. CDCs must master a myriad of fire, life safety, accessibility and building code requirements for all types of buildings. This credential is earned through the Door and Hardware Institute.

Change Key – A key that operates an individual cylinder.

Closer – See Door Closer. 

Closing Force (of a door closer) – Energy generated by a closer to close and latch the door.

Communicating Door and Frame – An opening that has a door installed in both rabbets of a double rabbet frame and each leaf swings in the opposite direction. Used to facilitate access as well as control of the opening. Commonly seen in hotel rooms. View Image

Conduit – A pipe or trough that carries electrical wiring, cables, etc.

Continuous Geared Hinge – A hinge that is the same length as the moving part to which it is applied and has interconnecting gears in lieu of a knuckle. View Image

Continuous Pin & Barrel Hinge / Piano Hinge – A hinge that is same length as the moving part to which it is applied but it has hinge knuckles in lieu of interconnecting gears. For example, the lid covering the keyboard of a piano is a Pin & Barrel Hinge. View Image

Contra-Swing Opening – A frame with two doors swinging in opposite direction and has a fixed or removable mullion between the doors. View Image

Control Key – A key used to remove the removable core from a removable core cylinder/lock.

Coordinator – A device used on a pair of doors to ensure that the inactive leaf closes before the active leaf. This device is necessary when both doors have closers and either of the following is true: 1) There is an overlapping astragal; or 2) The latchbolt of the active door needs to engage into the inactive leaf.

Core (of a door) – Material placed inside the door to provide either strength or fire ratings.

Corner Mullion / Corner Post – A closed frame section which facilitates a turn in the frame assembly. The most common degrees of turn are 45 and 90. View Image

Crossband – A ply placed between the core and face veneer of a wood door.

Curved Lip Strike – A strike with the lip curved to conform to the door casing or frame. This shape allows a smoother function of the latch while the door is closing.

Cylinder (of a lock) – The portion of the lock that receives the key. A cylinder contains the tumbler mechanism and the keyway which permits only the correct key to enter, turn, and operate the locking mechanism.

Cylinder Collar / Cylinder Ring – A trim or ring that fits under the head of a cylinder to allow adjustment, to give a trimmed appearance, and in some cases, to protect the cylinder from tampering.

Cylinder Set Screw – A screw, located under the armor front of a mortise lock, which keeps the cylinder stable within the lock. This screw also prevents the mortise cylinder from being removed unless the screw has been released.

Cylindrical Lock – A type of bored lock which has a cylindrical case or chassis to which the operating trim and a separate latchbolt attaches. Operation of the trim engages a retractor in the chassis which in turn, retracts the latchbolt.


Deadbolt (of a lock) – On a mortise lock, this is a supplementary bolt which has no spring action or bevel and is only operated by a key or a turn piece. This term is also used to describe a lock equipped with a deadbolt only. See Deadlock.

Deadlock – A lock equipped with a deadbolt only, and sometimes referred to as a deadbolt.

Deadlocking Latch Bolt – A two-piece latch bolt that incorporates the auxiliary dead latch into the latch bolt mechanism.

Delamination – Separation of plies or layers of wood or other materials through failure of the adhesive point.

DHI – Door and Hardware Institute is the association that serves door security and safety professionals in the non-residential construction industry. It provides education, advocacy, accreditation, and networking opportunities so that members can meet the security and safety needs of their customers.

Dogging (of an exit device) – A mechanism that fastens the cross bar or push pad in the fully depressed position and also retains the latch bolt(s) in a retracted position, thus permitting free operation of the door from either side.

Door Clearance – The distance between the top of the door and the frame rabbet at the head, the vertical edges of a door and the frame rabbet at the jambs, and the meeting edges of doors swinging in pairs. For the distance under the door see Floor Clearance and Undercut.

Door Closer – A device attached to the top of the door to regulate and control the operation of the door. See Mechanical Door Closer and Electromagnetic Door Closer.

Door Holder – A device that holds a door open at one or more selected positions.

Door Opening – The area within a frame into which the door or doors are installed.

Door Opening Height – The vertical opening in the frame for the door. It is measured between the door rabbet at the top of the door opening and the bottom of the frame. Also known as the nominal door height.

Door Opening Size – The measurement of the opening in the frame for the door. It is indicated as Door Opening Width by Door Opening Height. Also known as the Nominal Door Size.

Door Opening Width – The horizontal opening in the frame for the door. It is measured between the vertical jamb rabbets of the door opening. Also known as the nominal door width.

Door Position Switch – A switch used to monitor whether the door is an open or closed position.

Door Stop – As a hardware item, this is a device used to stop the swing or movement of a door at a certain point. On a frame, this term is used to define the part of a door frame against which the door closes. See stop.

Double Acting Doors – A door that swings in both directions. View Image

Double Egress Opening – A pair of doors swinging in opposite directions, located in the same plane within the frame. The doors are not separated by a mullion and are designed to facilitate traffic flow in either direction. View Image

Double Rabbet – A frame profile including two rabbets. View Image

Double Return – See Backbend.

Drywall Frame – A frame designed for installation in a wall constructed with studs and gypsum wallboard.

Drywall Profile – A frame with backbends.

Drywall Return – See Backbend.

Dummy Cylinder – A cylinder with no operating mechanism. It is used to cover cylinder preps on doors or for effect.

Dummy Trim – Non-operable trim that acts as a door pull.

Dust-Proof Strike – A floor-mounted strike with a spring plunger that covers the bolt hole when not in use. This is designed to minimize debris falling into the keeper of the strike.

Dutch Door – A door consisting of two separate leaves, one above the other. The bottom leaf may or may not include a shelf. View Image

Dutch Door Bolt – A device which locks together the upper and the lower leaves of a Dutch door.


Edge Guard – An angle or channel-shaped guard used to protect the edge of a door.

Edge Profile – A visual description of the vertical edge of a door. Typically referred to as beveled, bull nosed, rabbeted, or squared.

Edge Pull – A pull which is mortised into the edge of a sliding door.

Edge Seam – The connection of the face sheets at the vertical edge of a hollow metal door.

EHC – Electrified Hardware Consultant. This credential indicates that person is an expert at interfacing electrified architectural hardware products into access control monitoring and fire alarm systems, while maintaining compliance with fire, life safety, accessibility and building code requirements. The credential is earned through the Door and Hardware Institute.

Electric Strike – An electrical device that replaces a regular lock strike and permits releasing of the door from remote control or special access equipment, such as a card reader.

Electromagnetic Door Closer – This device combines a mechanical door closer with electromagnetic control to keep the door in a hold-open position. It is primarily used on fire rated doors that are desired to be held open since fire doors cannot be held open by mechanical means. It is electrically tied into the fire alarm system such that when the alarm is activated or there is power failure, the hold-open is released and the door closes.

Elevation – An orthographic projection of the vertical side of an assembly (doors, frames, etc.) usually shown on the architectural plans in conjunction with the vertical side view of a building wall.

Embossed Door – A door having a raised and/or indented pattern impressed on the surface.

Escutcheon (of a lock or exit device) – An elongated trim plate placed behind a knob or lever. The plate is usually long enough to span the height of a lock case with holes for thumbturns and cylinders.

Exit Device – A door-locking or door-latching device designed to provide fast and easy egress so building occupants can exit safely in an emergency. Egress is granted by pressing on a horizontal cross bar or push pad which releases the locking bolt or latch. An exit device on a non-fire rated door is also known as a Panic Device or Panic Hardware. On a fire rated door Fire Exit Hardware is needed.

Expandable Frame – See Adjustable Frame.


Face (of a door) – The surface of a door exposed to view when closed.

Face (of a frame) – The visible portion of the frame seen as you approach the door. That is, the area of the frame that is parallel to the face of the wall. View Image

Face (of a lock) – The exposed surface of a lock seen in the edge of a door. Also referred to as Armored Front, Edge Plate, or Scalp Plate.

Face Veneer (of a wood door) – The outermost exposed wood veneer surface of a veneered wood door.

Ferrous Metal – A metal containing or derived from iron. Ferrous metals are magnetic and give little resistance to corrosion.

Field Splice – A connection of hollow metal frame components accomplished in the field. Also referred to as a Shipping Splice.

Filler Plate – A metal plate used to fill unused mortise cutouts in a door or frame.

Fire Door Assembly – Any combination of a fire rated door, frame, hardware and other accessories that together provide a specific degree of fire protection to the opening.

Fire Exit Hardware – An Exit Device designed for use on fire rated doors.

Fire Rated – A product which has successfully met all conditions of acceptance of the fire test standard specified in the governing model or building code, is “Listed” or “Classified” and eligible for labeling by a recognized testing agency having a factory inspection service.

Fire Rated Door – The door component of a fire rated assembly. The specific fire resistance rating is displayed on an identifying label from a qualified testing and inspection agency. This label is permanently attached to the door.

Fire Rating – A numeric designation indicating the duration of fire test exposure to which a product has been exposed, and successfully met all acceptance criteria of the standard to which it is tested. For swinging door and frame products, typical fire ratings include 3, 1 ½, 1, ¾, and 1/3 hour.

Fixed Stop – See stop.

Fixed Transom – An inoperable panel or glass lite above a door opening.

Flat Lip Strike – A strike with a flat (non-curved) lip.

Floor Clearance – The distance between the bottom of a door and the top of the material directly below the door such as the top of the finished floor or the top of a threshold. Also referred to as the bottom clearance. (Note: This should not be mistaken as the Undercut.)

Floor Closer – A closing device installed in the floor under a door.

Flush Bolt – A door bolt designed so that when installed, it is flush with the face or edge of the door. This is typically used to secure the inactive leaf of a pair of doors.

Flush Cup Pull – A cup mortised flush into the face of a door. Typically used on sliding and bifold doors.

Flush Door – A door having no glass lites, panels, louvers or grills.

Flush Ring Pull – A cup mortised flush into the face of a door, which has a ring pull that folds flat into the cup when not in use.

Frame Member – A component in a frame such as a jamb, head, mullion, or sill.

Frame Profile – A visual description of a frame member. Typically referred to as cased open, single rabbet, double rabbet, and double egress.

Free Wheeling – A feature available on some locksets which allows the locked lever trim to rotate freely without retracting the latchbolt/operating the lock.

Front (of a lock) – the part of a lock visible in the edge of a door after installation. Also known as an Armored Front, Edge Plate, Face (of a lock), or Scalp Plate.

FRP Door or Frame – A door or frame made out of Fiberglass Reinforced Polyester. Also referred to as Fiberglass Reinforced Plastic.


Galvannealed Steel – Steel that has gone through the combined process of galvanizing and annealing. In addition to offering corrosion resistance, this steel has as improved formability, weldability, and has better paint adhesion than galvanized steel. This makes it an ideal choice in the hollow metal door and frame industry.

Gasketing – Material used to seal the perimeter of a door opening. Gasketing is applied for a variety of uses including environment control, sound control, light infiltration, smoke and fire control, etc.

Gauge – A numerical value used to describe the thickness of metal. Typical steel gauges for doors or frames are 12, 14, 16, 18, and 20. The smaller the gauge number, the thicker the material.

Glazing – The process of installing glazing materials.

Glazing Bead – The removable trim that holds glass firmly in place on a door or frame.

Grand Master Key (GMK) – A key that operates all of a large group of locks, which are in two or more master keyed groups.

Grouted Frame – A frame completely filled with the mortar or plaster used in wall construction.


Hand / Handing (of a door or frame) – A term used to indicate the direction a door swings. Handings are listed as Right Hand, Left Hand, Right Hand Reverse and Left Hand Reverse from the reference point of the security side of a door.

Handed Hardware – Hardware intended for use only on doors of the designated swing or handing.

Hardwood – Wood from trees having broad leaves, in contrast to trees with needles. This term does not refer to the hardness of the wood.

Hasp – A fastening device consisting of a loop and a slotted hinge plate, and is normally secured with a padlock.

Head (of a frame) – The horizontal member which forms the top of a frame. Also known as a header. View Image

High Pressure Decorative Laminate (HPDL) – A high impact laminate surface used for door faces.

Hinge – Hardware that is made up of two plates joined together by a pin and attached to a door and its frame. This serves to support or hang the door, and enables the door to swing.

Hinge Side (of a door) – See Pull Side of a door.

Hinge Types – Hinges are defined by their mounting method:

  • Full Mortise Hinge – Both hinge leaves are mortised – one into the door edge and one into the frame rabbet.
  • Full Surface Hinge – Both hinge leaves are surface applied – one to the door surface and one to the frame face.
  • Half Mortise Hinge – One hinge leaf is mortised into the door edge and one leaf is surface applied to the frame face.
  • Half Surface Hinge – One hinge leaf is surface mounted to the door surface and one leaf is mortised into the frame rabbet.

Hollow Metal – A term used to reference doors, frames, partitions, enclosures and other items, fabricated from sheet metal.

Hollow Metal Door – A door constructed of channel-reinforced sheet metal. The core of which is filled with some type of material to add desired properties such as structural integrity or insulation. Common metal door cores include honeycomb, polystyrene, polyurethane, steel stiffened, and temperature rise.

Hollow Metal Frame – A door frame constructed of sheet metal with reinforcing at hinges, strikes and other hardware.

Honeycomb Core – Used in hollow core wood doors and in hollow metal doors, this core is made from cellular shaped kraft paper.

Hospital Stop – The stops and soffit on a jamb or mullion of a door opening that are terminated at a specified distance above the floor and are closed square or at an angle. Used to facilitate cleaning the floor. Also referred to as Terminated Stop or Cut-Off Stop. View Image

HMMA – Hollow Metal Manufacturers Association (a division of NAAMM) develops standards, conducts product performance testing, and delivers education to promote the use of hollow metal doors and frames.


IBC – International Building Code is a model building code developed by the International Code Council (ICC).

ICC – International Code Council develops model codes and standards used in the design, build, and compliance process to construct safe, sustainable, affordable, and resilient structures. It publishes the International Building Code.

Inactive Door / Inactive Leaf – The leaf of a pair of doors that does not contain a lock, but instead contains a strike to receive the lock/latchbolt of the active door. When closed, the inactive leaf is typically secured by top and bottom bolts.

Indicator Button – A device used in a hotel lock or a privacy lock to indicate whether or not the room is occupied and the privacy feature is activated.

Integral Stop (of a frame) – A stop that is formed as part of the frame profile.

Intumescent – A material that expands when exposed to extreme heat or fire to fill any gap between the door and frame or between door leaves.

Invisible Hinge – A hinge designed such that no parts are exposed when the door is closed.


Jamb (of a frame) – The vertical frame components which form the perimeter of a hollow metal frame. View Image

Jamb Anchor – See Anchor.

Jamb Depth (of a frame) – The overall width of a frame member or profile. This is measured from the outside face to the outside face of the frame. View Image

Joint (of a door face) – The line of juncture between the edges or ends of two adjacent sheets of veneer.


Keeper (of a strike) – The portion of a strike plate or electric strike which receives the bolt or latch of a lock.

Kerfed Frame – A frame that is formed with an integral pocket or recess in the stop to receive gasket or seals. View Image

Key-in-knob / Key-in-lever (lock) – Used to describe the type of lockset which has the cylinder for locking and unlocking built directly into the knob or lever. Typically, these are bored locksets.

Key Side – A reference point used to establish the outside of a door when determining handing or for determining the secure side of glass bead.

Keyway – The shape or configuration of the hole in the lock mechanism that allows only a key of a particular shape to be inserted.

Kick Plate – A protective plate applied on the lower rail of the door to prevent the bottom of the door from being marred. Kickplates typically range in height from 8” – 16” (See also Armor Plate and Mop Plate.)

Knob (of a lock) – The portion of a lock which projects from a door and is grasped and turned to operate the lock.

Knocked Down Frame – A frame that is shipped in parts for assembly in the field. Commonly abbreviated as “KD.”

Knuckle – The enlarged part of a hinge into which the pin is inserted.

Knurling (on a lockset) – A series of small ridges or beads on the surface of the door’s operating trim for the purpose of providing tactile warning, to the visually impaired, that a door leads to a hazardous area. View Image


Label – A metal plate, sticker, or embossment on a product that indicates a performance level in accordance with a specific standard.

Labeled Door or Frame – In the aspect of fire resistance, this is a door or frame that conforms to all of the applicable requirements of a nationally recognized testing authority and bears a label designating that fire rating.

Latchbolt – The component of a lock which projects from the lock front and has a beveled end. The bolt is spring loaded but can be drawn back by operating the lock mechanism. When the door is closed, the latchbolt projects into a hole in the strike, which holds the door in a closed position.

Latching Speed (of a door closer) – The closing speed of a door closer that kicks in within the last few inches before the door reaches its latching point.

Lead Lined – A door or frame which is lined with lead to prevent radiation penetration.

Leaf – A single door or one of the doors in an opening that has multiple door leaves.

LEED – Leadership in Energy and Environmental Design is the certification given to buildings that meet specified benchmarks in green building.

Lever Handle (of a lock) – A horizontal handle that projects from a door and is used to operate the lock.

Lite – A glazed opening in a door which allows light to pass through.

Lip (of a strike plate) – The projecting part of a strike (either curved or flat) on which the latch bolt rides. It projects beyond the face of the frame and is the first part of the strike plate that the latch bolt will hit.

Lock Block (in a wood door) – Reinforcement blocking concealed in the door adjacent to the stile at the lock location.

Lock / Lock Set – A complete lock or latch assembly, which includes the lock/latch mechanism and the trim – such as knobs, levers, escutcheons, or roses.

Louver – A series of slats, blades, or piercings to allow passage of air through an opening.


Master Key (MK) – A key that operates a group of locks, each of which is also operated its own individual change key.

Mechanical Door Closer (hydraulic) – This device combines a spring and a compression chamber into which liquid slowly moves through chambers. The liquid and compression chamber regulate the spring which provides a means of controlling the opening speed and the closing action.

Medium Density Fiberboard (MDF) – A composite made from highly refined wood fibers. This can be used as a wood door core or to produce molded panel face sheets.

Medium Density Overlay (MDO) – A resin impregnated paper that is applied as the outer face of a wood door to provide the optimum surface for painting.

Meeting Edges – Two adjacent door edges not separated by a mullion or transom bar. These are found in pairs of doors, Dutch doors, and door and transom applications.

Meeting Stile – The vertical edge of a door, in a pair, which is adjacent to the other door. Also known as the Meeting Edge.

Mineral Core – A non-combustible core of mineral composition such as gypsum. This core is typically used in wood fire doors having ratings from 45 – 90 minutes.

Mop Plate – A narrow plate similar to a kick plate. It is mounted to the bottom of the door and is high enough to protect the door against the swish of the mop or dings from vacuum cleaners. Mop plates are typically 4” or 6” tall.

Mortise – The cavity made to receive a lock or other hardware. This term can also refer to the act of making such a cavity.

Mortise Lock / Mortise Latch – A lock assembly designed to be installed into a mortise in the edge of a door rather than into a bore or applied to the door’s surface.

Mullion (of a frame) – A fixed or movable frame member which separates door leaves, a door and sidelites, glazed areas, or paneled areas. View Image

Muntin – A bar or formed material supporting and separating panes of glass within a door, sidelite, transom, borrowed lite, or window frame.

Mute – See Silencer.


NAAAM – National Association of Architectural Metal Manufacturers represents architectural metal products for building construction, including the development and distribution of technical standards.

Narrow Side (of a door) – See Push Side of a door.

Net Door Size – See Actual Door Size.

Neutral Pressure – A fire door test procedure where the neutral pressure plane is near the top of the door.

NFPA – National Fire Protection Association is a global non-profit organization that is devoted to eliminating death, injury, property and economic loss due to fire, electrical, and related hazards.

Nominal Door Size – See Door Opening Size.

Non-Ferrous Metal – A metal that does not contain iron, is not magnetic and is usually more resistant to corrosion that ferrous metals. Examples of non-ferrous metals are aluminum, copper, brass, and stainless steel.

Non-Removable Pin (of a hinge) / NRP – An optional feature where the pin of the hinge is fastened securely in place, preventing separation of the two leaves.

NWWDA – National Wood Window and Door Manufacturers Association. This organization was renamed WDMA in 1998. See WDMA.


Opening Force (of a closer) – The force required to open a door against the closer’s spring power.

Opening Size – See Door Opening Size.

Overhead Concealed Closer – A door closer concealed in the head of a frame or in the top rail of the door, with an arm that connects the door and the frame.

Overlapping Frame – A frame which wraps the wall structure rather than butts against it. View Image


Pair (of doors) – Two doors in the same frame and not separated by a mullion.

Panic Device – See Exit Device.

Panic Hardware – See Exit Device.

Particleboard Core – A composite wood door core consisting of small particles of agri-fiber or wood fiber.

Piano Hinge – See Continuous Pin and Barrel Hinge.

Pin Tumblers – Small sliding pins in a lock cylinder working against coil springs and preventing the cylinder plug from rotating until the pins are brought to proper alignment by the bitting of the correct key. View Image

Pivot Hinge – A door hanging device consisting of a fixed pin and a single joint. Types include center hung and offset hung. View Image

Plug (of a lock cylinder) – The round part of the cylinder containing the keyway and when rotated by the key transmits motion to the bolt(s) or other locking mechanism.

Pocket Door – A door that slides into and out of a recess in the adjacent wall.

Polystyrene Core – A hollow metal door core made from preformed Styrofoam.

Polyurethane Core – A hollow metal door core made from expanded rigid foam which is either foamed in place or preformed.

Positive Pressure – A fire door test procedure where the neutral pressure plane is located at 40 inches above the sill.

Prefit (of a door) – Undersizing and beveling of a door to fit into a door frame.

Prehung Door and Frame – A door that is already assembled and hanging in its own frame prior to shipment.

Profile (of a frame) – The shape that makes up the cross-section of a frame.

Pull Side (of a door) – The face of the door opposite the frame stops. Also referred to as the Hinge Side or Wide Side.

Push Plate – A plate applied to the lock stile of a door to protect it against soiling and wear from persons pushing the door open.

Push Side (of a door) – The face of the door which contacts the frame stops. Also referred to as the Stop Side or Narrow Side.


Rabbet (of a frame) – The area between the stop and the face of the frame and is capable of accepting a door, panel, or glazing. View Image

Rabbeted Door Edge – A door edge formed to interlock with another door, frame, or panel. View Image

Raceway (in a door) – A pathway that provides access for wiring, tubing, or cables through the door.

Rail (of a door) – The horizontal member forming the top or bottom edge of a door, or separating panels or glazed areas in the door. Referred to as Top Rail; Intermediate, Mid or Center Rail; and Bottom Rail. View Image

Removable Core Cylinder / Interchangeable Core (IC) – A cylinder containing a core assembly that is easily removed without disassembly of the lock. This core assembly incorporates the entire tumbler mechanism including the plug, tumblers, and separate shell. The cores are removable and interchangeable by use of a special key, called a Control Key. View Image.

Removable Mullion (of a frame )– A frame member which can be removed temporarily to allow large objects to pass through.

Removable Stop (of a frame) – A metal channel or angle which is removable to allow installation of a door, glass or a panel.

Return – The element of the frame profile which extends inward from the face to the throat. View Image.

Reverse Bevel – Refers to the hand of a door when the door swings to the outside/keyside.

Reversible Lock – A lock that may be used in any hand, by reversing the latch bolt. On certain types of locks, other parts must also be changed.

Rim Cylinder – A cylinder mounted through the door independently of the lock and installed with long screws that hold the cylinder in the door from the inside. The lock mechanism is engaged by a tailpiece connected to the rim cylinder. View Image.

Rose (of a lock) – A trim plate, usually disk or oval shaped, placed behind the knob or lever of a lock or latchset.

Rough Opening – The size of a wall opening into which a frame is to be installed.


SDI – Steel Door Institute is a non-profit business association that develops quality and performance standards for steel doors and frames.

Shipping Bar – See Spreader Bar.

Shipping Splice – See Field Splice.

Sidelite Frame – A framed area immediately to one or both sides of a door opening which contains fixed glazing or panels.

Silencer – A piece of resilient material attached to the stop of a frame to cushion the closing of a door. Also referred to as a door Mute.

Sill (of a frame) – The bottom horizontal member of a sidelite or borrowed lite frame. Also referred to as the Base. View Image.

Single Acting Door – A door which only opens in one direction.

Single Rabbet Frame – A frame profile containing only one rabbet. View Image

Slip Match – The practice of placing two or more adjoining wood veneer surfaces in sequence so the same face sides are exposed.

Soffit (of a frame) – The element of a door frame between the stops on a double rabbeted frame, and the stop and the largest face on a single rabbet frame. Also referred to as the “Stop Width.” View Image

Spat – A protective covering, usually stainless steel, applied over the bottom of frame jambs to reduce damage to the fame.

Spindle (of a lock) – The bar connected with the knob or lever handle that passes through the hub of the lock. As the knob or lever handle is used, the spindle rotates and engages the mechanism to operate the latchbolt.

Split Frame – See Adjustable Frame.

Spreader Bar – A metal channel or angle temporarily attached to the base of a door frame, extending between jambs, to keep the frame in proper alignment during shipping and handling. Also known as a Shipping Bar.

Spring Hinge – A hinge containing one or more springs to move the door into a closed position.

Squared Edge (of a door) – A door edge that is formed 90 degrees to the face of the door. View Image

Stave Lumber Core (SLC) – A wood door core made of solid blocks of wood with the end joints staggered in adjacent rows and bonded together.

Steel Stiffened Core/Vertical Stiffened Core – A core made out of metal stiffeners welded to the face skins of a hollow metal door.

Stile (of a door) – The outermost vertical members of the door structure. View Image

Structural Composite Lumber Core (SCL or SCLC) – A composite wood door core made by fusing hardwood strand board from a variety of tree species.

Stop (of a frame) – The portion of the frame that the door closes against or panels and glass sit against. Also see Integral Stop and Removable Stop. View Image.

Stop Side (of a door) – See Push Side of a door.

Stretcher Plate – A protection plate similar in size to a kickplate, but mounted at a height to protect the door from gurneys and hospital beds.

Strike Plate – A metal plate or box that is pierced or recessed to receive the projected bolt or latch of a lock. It is sometimes called a Keeper.

Swaging (of a hinge) – A slight offset of the hinge leaves at the barrel, which permit the leaves to come closer together. View Image

Sweep (of a door closer) – The movement of the door from the open position to the point where it is a few inches away from hitting its latching point.


Telegraphing – A wood door defect where the internal components of the door show through the face veneer.

Temperature Rise Rated Door – A fire rated door designed to limit the transfer of heat to within a specified temperature over a specified duration.

Terminated Stop – See Hospital Stop.

Threshold – A strip fastened to the floor beneath a door, and is usually required to cover the joint where the two types of floor material meet.

Throat (of a frame) – The opening between the back bends/returns of a frame profile. On frames that wrap a wall, the throat must be large enough to accept the wall thickness. View Image

Throw (of a lock) – The distance a latchbolt or deadbolt projects when fully extended.

Thumb Piece (of a lock or exit device trim) – The small pivoted part above the grip of a handle that is pressed by the thumb to operate a latch bolt.

Thumbturn – An oval or crescent shaped knob/lever used to operate a deadbolt. Also known as a Turn Piece.

Tolerance – The permissible deviation from a nominal or specified dimension or value.

Transom – A framed area immediately above a door opening which contains fixed glazing or panels.

Transom Bar (of a frame) – The horizontal frame member/mullion that separates a door opening from a transom.

Tubular Lock – A type of bored lock that contains three components: 1) An outside knob/lever, rose and spindle assembly, 2) a latch unit, and 3) an inside knob/lever and rose assembly. The latch is operated by a spindle attached directly to the inside and outside handles.

Turn Piece (of a lock) – See Thumbturn.

U / V / W 

UL – Underwriters Laboratories is an independent product safety certification organization that tests products for safety and performance. A product with a UL mark demonstrates that the product is in compliance with the named safety standard.

Undercut – The distance between the bottom of the door and the bottom of the frame. (Note: This should not be mistaken as Floor Clearance.)

Veneer (wood) – A thin sheet of wood, rotary cut, sliced, or sawed from a log, bolt, or flitch.

Vision Light or Vision Panel – A glazed opening in a door. Also referred to as a Lite.

WDMA – Window and Door Manufacturers Association defines the standards of excellence in the residential and commercial window, door, and skylight industry and provides resources, education, and professional programs to its members.

Weephole – An opening provided in a hollow metal door to allow for the drainage of moisture.

WH (Intertek) – Warnock Hersey Intertek is an independent product safety certification organization that tests products for safety and performance. The WHI mark demonstrates a product’s compliance to safety and/or performance standards.

Wicket Door – A swinging door within a door. View Image

Wide Side (of a door) – See Pull Side of a door.