A
Active Panel
The main moving panel in a door unit, typically the one used most frequently for entry and exit.
Aluminum Surround
A metal framework, usually aluminum, that encases a screen or energy panel for structural support and clean edge finishing.
Apron
The horizontal trim piece located beneath the window stool, adding a decorative element to interior window framing.
Argon Gas
An odorless, inert gas inserted between glass panes in insulated units to enhance thermal efficiency and reduce heat transfer.
Assembly
A grouping of two or more window or door units that are factory or field-mulled together to create a larger configuration.
Astragal
A vertical molding attached to the meeting edge of one door panel (usually on French doors), providing overlap and sealing when closed.
Authentic Divided Lites (ADL)
Also called True Divided Lites; individual panes of glass separated by permanently fixed muntins in the sash or panel.
Awning Window Unit
A top-hinged window that swings outward from the bottom, allowing ventilation even during rain.
B
Balances
A counterbalancing system, usually block-and-tackle style, used inside the frame to assist in opening and holding double or single hung window sashes in place.
Bars
Horizontal or vertical components in a divided lite window or door that separate and hold individual panes of glass.
Bay Windows
A projection window feature composed of three or more windows that angle outward from the building, often with a central fixed window and two flanking operable units.
Blindstop
An interior trim piece placed between the window jamb and the casing, creating a stop for screens or storm panels.
Bow Windows
A curved, multi-panel window that forms a graceful arch shape, usually composed of four or more units.
Brick Mould Casing (BMC)
An exterior trim that wraps around a window or door frame and overlaps exterior siding, providing both aesthetic and functional sealing.
C
Cam Lock
A locking mechanism that engages by rotating a lever to secure sash in place, most commonly used in sliding or double hung windows.
Cam Pivot
A pivot pin system attached to the sash stile, resting on the balance mechanism to enable sash movement in double or single hung units.
Capillary Tubes
Tiny tubes inserted in the spacer of insulating glass to equalize pressure in varying altitudes and prevent stress on the glass.
Casement Window
A side-hinged window that opens outward with the turn of a crank handle; often used for unobstructed views and full ventilation.
Cladding
An exterior aluminum or vinyl covering applied to wood windows or doors to improve durability and reduce maintenance.
Combination Door
An additional framed panel with removable glass and screen inserts, mounted on the exterior side of a main door.
Cottage Window
A window style where the upper and lower sashes are not the same height, usually with a smaller upper sash.
D
Daylight Opening (DLO)
The actual visible portion of glass through the frame—measured width by height.
Direct Glaze
Glass that is permanently set into the frame without a sash, creating a stationary window.
Divided Lites
A window or door design that breaks up the glass surface into smaller sections using muntins or grilles—either physically or visually.
Double Hung
A window with two operable sashes that move vertically within the frame, offering top and bottom ventilation.
Drip Cap
An exterior metal or vinyl trim installed above a window or door to deflect water away from the top of the frame.
E
Electric Operator
A motorized system that opens or closes windows (typically awnings or casements) via switch or remote control.
Energy Panel (EP)
A removable secondary glass pane used to improve energy performance by adding another insulating layer.
Escutcheon
A decorative plate or trim behind door hardware like handles or levers, often used to cover the hardware mounting area.
Extrusion
A shaped material (often aluminum or vinyl) made by pushing it through a mold—used for frames, cladding, and other components.
F
Finger-Joint
A woodworking technique where interlocking fingers are cut into pieces of wood and glued to form a longer, stronger board.
Flanker
A side window placed next to a larger center unit, often used in bays or combined window assemblies.
Footbolt
A floor-activated bolt mechanism used to secure an inactive door panel or screen in the closed position.
Frame
The fixed structural component of a window or door that encloses the sash, panel, or glazing.
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