Home improvement projects can be somewhat intimidating, especially if you don’t know exactly what product or solution you need. Our goal at Zabitat is to help customers put the pieces of their curb appeal project together step-by-step. Our Home Improvement glossary provides the most common millwork (door and window) terms — aimed at helping you connect the dots, and finding the perfect product for your home.


Active: In paired or double doors, the hinged door leaf which is primarily operable.

Affidavit Label: For fire-rated doors, a label on a door product on which the manufacturer, not an independent laboratory, states that the door meets a type or types of test criteria.

Air Infiltration: Air passing through a door system when the door is under pressure, usually from wind.

Annealed Glass: Regular glass which has not been heat strengthened or tempered. Most window glass is annealed.

Astragal: The post-type fitting on the latch-side edge of one of a set of paired or double doors, which covers the margin between doors when they are closed, and which houses or contains the weatherstrip.

Backset: For locating a machined hole, recess, or mortise, the distance from an edge or surface to the center or edge of the recess, hole or mortise.

Ball-bearing Hinge: A heavier-duty hinge than the standard hinge, with bearings supporting the pivots. Ball-bearing hinges are usually used for heavy doors that will be in commercial or industrial use.

Barbed: An adjective that describes the feature of a part which inserts into a slot, and which has surface features that enable it to stay firmly inserted into the slot.

Boot: A term used for the rubber part at the bottom or top end of an astragal, which beds the astragal end and seals between the end and the door frame or sill.

Boss, Screw Boss: A feature of a part which enables the fastening of a screw into the feature, thereby allowing assembly of the part with another. Screw bosses are common features of molded plastic lite frames and extruded aluminum door sills.

Box-Framed: In door and sidelite assemblies, a term used to differentiate door and sidelite units which are first framed as separate units, with heads and sills separate and the width of the door or sidelite panels. Box-framed doors are joined to box-framed sidelites.

Brad: A small nail with a small head, usually used to fasten small trim and moldings.

Brickmould: A molding, used to trim the outside edge of a door frame. Brickmould is most often applied to prehung units.

Buck: A term usually used in masonry construction to describe a door frame or a subframe in a masonry opening, around which a steel door frame wraps and is fastened.

Butt: A type of hinge commonly used to assemble doors. Butt hinges are often referred to as simply butts.

Butyl: An organic compound, used in the door business as a sealant. It is naturally black, and is heated and pumped through nozzles, or pumped cold.


Came, Caming: Formed metal stripping, usually made of brass or zinc plated steel, used between cut-glass pieces to assemble the pieces into a decorative glass panel. Caming is soldered at joints to bond the glass assembly together.

Carpet Shim: A spacer block used under a door sill to raise the sill an appropriate amount if carpet is used, so the door panel clears the carpet when opened.

Casing: A horizontal or vertical molding, which accents or trims edges of doors and windows to the surrounding walls. Casing also covers or accents intermediate posts.

Caulking: Sealant which is usually extruded or troweled into a recess or joint, to seal against air and water leakage through the joint.

Clad: Provided with a facing or jacket which works as a protection against weather, and provides a finished appearance. Cladding may be painted metal, plastic, or a heavy coating applied by the manufacturer.

Clear Jambs: Natural wood door frames, without paint or primer applied, and which appears to be made of full-length pieces of stock, without joints or knots.

Closed-Cell Foam: Sponge-like material, usually used in gaskets and weatherstripping, which compresses into joints, but absorbs little water.

Closer Block: An inside reinforcement, usually placed across the top edge of a door, to enable firm fastening of self-closing hardware to the door.

Condensation: Condensation, or “sweating”, is a natural occurrence in the home and is caused by excessive humidity, or invisible water vapor, present in the air. When this water vapor comes in contact with a surface which is at a cooler temperature, the vapor turns to visible droplets of moisture. Often this harmless water vapor can be seen collecting on glass surfaces, such as windows or doorglass.

Continuous Sill: A sill used for a type of door and sidelite unit in which the unit has full width top and bottom frame parts, and an internal post or posts separating sidelites from the door panel.

Core: The center section or part of a door or door part.

Corner Plug, Corner Seal Pad: A small part, usually made of resilient material, used to seal water which gets beyond the bottom ends of weatherstrip in doors, from getting between the door edge and the jambs, adjacent to the bottom gasket.

Cove Molding: A small molded wood lineal piece, usually formed with a scooped face, used to trim and fasten a panel of some type into a frame.

Crossbore: A large through-hole, near the edge of a door panel, usually 2-1/8 inch in diameter, which houses a cylinder lockset or deadbolt latch.

Cylinder Lock, Cylindrical Lock: Lock hardware which mounts into a door which has been prepared with a bored hole or holes through the face, and into the edge.


Dado: A machined or sawn groove, across the width of a part.

Deadbolt: A latch used to secure a door closed, the latch being driven from the door into a receiver in the jamb or frame.

Deflection: The distance a door has moved away from its closed and latched position, usually measured at the top unsupported latch-side corner. Deflection may be caused by wind pressure or heat. Deflection is temporary. The door returns to position when the force is removed.

Desiccant: Moisture absorbing material used inside the spacer in an insulated glass assembly, so as to control moisture levels and prevent moisture from frosting or condensing on the inside glass surfaces of the insulated unit.

Doorglass: An assembly of frame and glass panel, which when fitted to a door in a formed or cut-out hole, creates a door with a glass opening.

Doorlite: An assembly of frame and glass panel, which when fitted to a door in a formed or cut-out hole, creates a door with a glass opening.

Double-Glazed: Outfitted with two panes of glass with a sealed airspace between.

Drip Strip: In exterior doors, a fitting used across the outside face of the door adjacent to the bottom edge, to divert cascading rain away from the door bottom edge and away from the door/sill joint.

Drywall Opening: A rectangular opening in a wall, usually an interior wall, prepared to the size necessary to receive a pre-hung assembly.

DSB Glass: A term no longer used in the glass business, which meant “Double Strength, ‘B’ quality.” DSB glass when furnished by Therma-Tru in doors, is 1/8-inch thick, single pane and not insulated.

Dummy Cylinder: A lock without a latch, typically used for the passive door panel of a double door unit, so that the hardware appears equal to that used on the active panel.


Edge Bore: The hole bored through the edge of a door to allow the latch to pass through, into the strike.

Electric Strike: A mechanism which allows a switch to open the latch of a door.

End Seal Pad: A closed-cell foam piece, about 1/16-inch thick, in the shape of a sill profile, fastened between the sill and the jamb to seal the joint.

Escutcheon: A stamped decorative plate, usually circular to trim the shaft of a door knob or deadbolt latch, to trim the opening where the shaft or latch adjoins the face of a door.

Etched Glass: Glass used for doorlites on which a decorative pattern is engraved by means of chemical action or mechanical sand-blasting.

Extension Unit: A framed fixed door panel, with a full-sized lite of glass, field-installed or shop-installed adjacent to a two-panel patio door, to make the door unit into a three-panel door.


Faceplate: The plated or solid metal trim piece, usually about 1 x 2-1/4 inches, housed flush into the edge of a door, through which projects the latch of a passage lock or deadbolt.

Finger Joint: A way of joining short sections of board stock together, end to end to make longer stock. Door and frame parts are often made using finger-jointed pine stock.

Fire Door: A door of a construction type which has been tested to contain the spread of fire from one room or occupancy area to another. Fire doors are listed and labeled to show their ratings in terms of time, i.e., 20-Minute, 90-Minute, etc.

Flush-Glazed: A type of glazed door which has its glass perimeter moldings flush with or set down from the face of the surrounding door.

Foam: Rigid or flexible plastic, light in weight and cellular in structure, used in door construction. Rigid foam is used as the insulating and binding core for doors. Flexible foam is sometimes used as gasket.

Foot Bolt: A steel pin housed in a door bottom edge or astragal, with a latch mechanism, which can be driven down to project into a receiver socket or hole in the floor or threshold, to better secure the door when closed.

Frame: In door assemblies, the perimeter members at the top and sides, to which the door is hinged and latched. See jamb.


Gain: A notch across the end of a board or wood part.

Galvanized: An adjective used to describe steel which has been zinc-coated. Galvanized steel is resistant to corrosion.

Gasket: A strip of flexible material which in an assembly of parts, prevents air and water from penetrating or passing through joints between parts.

Glazing: The elastic material used to seal glass to a surrounding frame.

Grille: For doors with glass lites or inserts, a removable face-mounted assembly of thin wood or plastic pieces, which when in place, gives the lite or insert a patterned multi-pane look.

Grooved Glass: Glass which has been decorated with abrasively-routed recesses. Grooving can give a single piece of glass a multi-paned look.


Handing: A term which describes or determines the direction of swing of a door when opening.

Head Bolt: A steel pin housed in a door top edge or astragal. See foot bolt. Head, Head Jamb: The horizontal top frame member of a door assembly.

Hinge: An assembly of metal plates and a cylindrical metal pin, which when fastened to a door edge and to a door frame, allow the door to swing or rotate in its frame.

Hinge Stile: The full-length vertical edge of a door, at the side or edge of the door which fastens to its frame with hinges.

Horned Sill: A sill which has been coped or cut in such a way at its ends, so that the sill projects across the outside face of the bottoms of door jambs, allowing the bottom ends of the brickmold pieces to butt and join to the top of the sill.


IG Unit: Abbreviation for insulated glass unit.

Inactive: A term for a door panel fixed in its frame. Inactive door panels are not hinged and are not operable.

Insulated Glass, Insulating Glass: A glass assembly of multiple full-lite pieces, separated by a perimeter spacer and sealed as a unit. Insulated glass in residential doors is usually made with two thicknesses of 1/8-inch glass, separated by an airspace
up to 3/4-inch thick.

Inswing: A term used to describe an exterior entry door unit for which, when the hinged door panel is opened, the panel swings into the building.


Jamb: A vertical perimeter frame part of a door system.

Jamb Jack: A fastener device for fixing a door frame to a wall structure, which allows the space or margin between the frame and the structure opening, to be varied by turning the fastener screw.

Jamb Stop: In exterior door frames, the molded-in rebate surface of a frame member against which door panels close and seal.

J-channel: Installed or built-in to the side of a door, this channel is designed to accommodate the ends of siding pieces to provide a finished appearance.


Kerf: A thin slot cut into a part with a molder or saw blade. Weatherstrip is inserted into kerfs cut into door jambs.

King Stud: In a wood-framed rough opening, the stud which runs full height from floor plate to ceiling plate, against which trimmer stud attaches.

Knuckle: The feature of a hinge where the hinge leaf is cut for two or three projections which wrap and form a barrel or socket for the hinge pin.


Laminate: A thin face of wood or plastic, adhesively bonded to a core or substrate, which makes up the decorative, wear or weatherable surface of the part.

Latch: A moveable, usually spring-loaded pin or bolt, which is part of a lock mechanism, and engages a socket or clip on a door jamb, retaining the door closed.

Leaf: A term which can apply to a door or hinge and which defines a part of the assembly which can swing on a pivot. Butt hinges have two leaves.

Lite: An assembly of glass and a surrounding frame, which is assembled to a door, or is integrally built into the door at the factory.

Lock Block: A rectangular block of wood or other solid material, placed inside a door assembly at the lock side edge, which reinforces the assembly when the lock hardware is installed.

Lock Bore: For cylindrical locksets, the large through hole, usually 2-1/8-inches in diameter, bored near the door panel’s lock edge, into which the lock mechanism is placed and installed.

Lock Stile: In insulated door assemblies, the full-length part, usually wood, which makes up the lock edge of the door panel. In wood stile and rail doors, the full length wood piece, 4 to 6-inches wide, at the lock edge of the door.

Low-E Glass: Glass which has been factory coated with a thin layer of material, nearly clear, which acts to absorb and reflect heat and light energy.

LVL: Abbreviation for laminated veneer lumber. LVL is a manufactured wood product, in which veneer layers are adhesively bonded into a layup of multiple thicknesses. LVL is made to specified strengths and is used for structural purposes.


Miter: An angled cut across the end of a lineal part, usually done to join with a similarly-cut part at a corner.

Mortise: A recess cut into the surface or edge of a part, usually for the purpose of housing hardware such as hinges and lock parts.

Mortise-Type Lock: A lockset which usually has a rectangular-shaped mechanism, which is housed into a deep recess cut into the edge of a door.

Mull: A short term for mullion. Used occasionally as a verb to describe the joining of two door units together, or the joining of a door to a sidelite unit.

Mulled: An adjective describing a door and sidelite unit which has been made up by edge-joining two framed units together.

Mullion: A post or divider which runs from sill to frame top in a multi-panel door, door, or door and sidelite assembly. In stile and rail doors, the vertical wood parts which separate panels.

Multiple Extension Unit: In patio door assemblies, a fixed door panel in a separate frame, edge-joined to a patio door unit to add another glass panel to the installation.

Muntins: In glazed lite assemblies, thin vertical and horizontal divider bars, which give the lite a multi-paned look. Muntins may be part of lite frames, and on the outside surface of the glass, or assembled between glass in insulated glass units.


Nailing Fin: A feature of some windows and patio doors which permits installation and fastening to a rough opening by nails or screws driven through the fin at the top and side edges of the unit, into the surrounding frame of the opening.

NFRC: Initials for National Fenestration Ratings Council, an industry association which sets standards for testing, rating, and labeling doors and windows with heat transmission and energy information.

Night Latch: A lever or knob-actuated bolt for fastening a door more securely at night.

Nosing: An edge piece, usually molded with a rounded face or corner, which runs the length of an assembly. Oak adjustable sills have a nosing part along the floor line at the inside edges.

NRP Hinge: An abbreviation for a hinge with a non-removable pivot pin. NRP hinges are used when exterior doors swing out, as a security feature. The fixed pins make it impossible to remove a door by driving out pivot pins.


Open-Cell Foam: A foam material which has passageways between cells. Open-cell foam will absorb and retain water, because the water will penetrate deeply inside the foam.

Outswing: An exterior door assembly in which the door panel swings outside the building.


Panic-proof Lock: A lock and latch device which permits a door to be opened outward by pressure being applied to a bar mounted across the inside face of the door.

Passage Lock: A lockset which will retain a door closed, but which cannot be locked.

Passive: In a double or two-panel door assembly, the door which usually remains closed and fixed by bolts at top and bottom. The other door panel is used for regular passage.

Plant: A decorative molding applied to the surface of a flush door, to give the appearance of a raised-molding design.

Plates: In residential wood-frame construction, the horizontal parts of a wall frame running atop the subfloor, and at the ceiling atop the stud ends, on which framing from above bears.

PVC: Abbreviation for polyvinyl chloride, a plastic material used to make molded or extruded parts.


R-Value: A number which describes in relative terms, the ability of a material or assembly to resist the flow or transmittance of heat. Assemblies or materials with high R-values are better insulators than those with lower R-values.

Rabbet, Rebate: A rectangular recess cut or formed along the long edge of a part, usually a wood part.

Rail: In insulated door panels, the part, made of wood or a composite material, which runs inside the assembly, across the top and bottom ends, and makes up the top or bottom edge. In stile and rail doors, horizontal pieces at top and bottom edges, and at intermediate points, which connect and frame between the stiles.

Ramp: In a sill or threshold, the horizontal face which is sloped.

Rebate: See rabbet.

Reveal: The offset or margin between edges of parts.

Riser: A term which describes the part of an adjustable sill which can be moved up or down by turning adjusting screws.

Riveted-Pin Hinge: See NRP hinge.

Rough Opening: A structurally-framed opening in a wall which receives a door unit or window.


Saddle: In adjustable sills, another term for riser. Also, a shop-applied label applied around the corner or edge of a door, which provides identification and installation instructions.

Safety Glass: Glass which when broken, shatters into small pieces without sharp edges.

 A line (as a scratch or incision) made with or as if with a sharp instrument.

Screen Track:
 A feature of a door sill or frame head which provides a housing and runner for rollers, to allow a screen panel to slide from side to side in the door. Scribe: A mark for a cut which has been made by using a template or pattern.

Sealant: Elastic material pumped or troweled into a joint to prevent water penetration.

Self-Cased: A steel frame for which the edge detail finishes to the surrounding wall, without the need for additional applied casing molding.

Self-Locating Hinge: A hinge with indexing or locating tabs to aid in exact placement against a door edge.

Shim: A thin piece of material used between parts of an assembly, to change and fix the distance between parts, when parts are fastened.

Sidelite: A fixed narrow panel, installed next to a door panel, for decorative purposes. Sidelites almost always contain glass lites.

Sill Saddle: See riser.

Slide Bolt: The part of an astragal assembly which, by means of moving latches at tops and bottoms of astragals, places bolts into frame heads and sills, for fixing passive door panels closed.

Smoke & Draft Door: Where building codes define use, a fire door which has been rated for 20-minutes fire resistance, and which does not need test certification as having passed the hose stream portion of the fire test.

Spacer, Glass Spacer: A lineal part with rectangular cross section, running along the perimeter edges, between the glass pieces of an insulating glass unit.

STC: Abbreviation for sound transmission coefficient. A value which describes in relative terms the ability of a door to dampen the passage of noise. Doors with higher STC values permit less noise to pass through.

Stile: In insulated door panels, the full-length parts, usually wood, which make up the long edges. In stile and rail doors, the vertical edge parts.

Strike: A metal part with a hole or recess for receiving a door latch, also with a curved or ramped face so a spring-loaded latch contacts it when closing. Strikes are fit into mortises in door jambs or mullions, and screw-fastened.

Style: A number or name defining a door design or configuration.

Subfloor: The concrete or wood floor surface lying under the finished floor. Prehung door assemblies are installed atop the subfloor.

Substrate: The base or core material in an assembly of parts. In sills, the full length wood or composite part of the sill, visible only from the bottom side, or ends.


Tempered Glass: Glass sheet which has been strengthened by heat processing. Tempered glass when broken, shatters into small pieces without sharp edges. See safety glass.

Template: A pattern or jig used to machine-cut a precise hole or recess into a door or frame part.

Thermal Break: A feature of a door or frame assembly which separates metal or glass exposed to outside temperatures, from coming into contact and transmitting heat to or from inside-exposed parts.

Threshold: Another term for sill. The horizontal part of a door assembly, fixed under the door panel and bearing on the floor.

Tinted Glass: Glass made with a green, gray or bronze tint, so as to reduce light transmittance.

TPE: Abbreviation for thermoplastic elastomer. TPEs are used to make weatherstripping and gasketing parts.

Transom: A framed glass assembly mounted atop a door assembly. Transoms are rectangular in shape or have curved or arched tops. One design of a curved top transom has the shape of a half-ellipse.

Transport Clip: A steel piece used to temporarily fasten a prehung door assembly closed for handling and shipping, which maintains the door panel’s proper position in the frame.

Trimmer Stud: In a wood-framed rough opening, the stud or framing member which runs vertically from the subfloor to and supporting the structural header member, into which a door frame is fastened.

Triple-Glazed: An insulated glass assembly made of three thicknesses of glass, with air spaces between the outer and inner thicknesses.


U-Value: A number which describes in specific terms, the ability of a material or assembly to transmit heat from outside to inside surfaces. Assemblies with lower U-values transmit less heat than those with higher values. SeeR-value. A U-value is the inverse of an R-value.

Urethane: A plastic material made by reacting two polymers. A urethane part will burn, but it will not melt.

Veneer: A thin film or facing, adhesively bonded to a core or substrate, which makes up the exposed and decorative face of an assembly.


Warp: A permanent curvature or deviation from straightness, which can be induced in a part or assembly by a load or force, or by exposure to heat or moisture.

Water Penetration: The unwanted passage of water through a door system.

Wired Glass: Glass made for use in fire doors, which has embedded wires which bind the glass, and permit the glass to remain monolithic when exposed to fire.


Yellow Zinc Dichromate: A brass-look plating to steel parts, which is highly corrosion-resistant.