The Fenestration Glossary

TERM	MEANING
jack stud	Vertical framing members, generally 2x4’s, which form the inside of the window or door rough opening. They support the header and run down to the sole plate.
jamb	The main vertical members forming the sides of a window or door frame. Side jambs are the vertical pieces of a window frame. The head jamb is the horizontal piece across the top. The vertical member of a window frame.
jamb liner	In a modern double-hung window, the track installed inside the jambs on which the window sashes slide. Vinyl or metal covering applied to the side jambs of double hung and single hung windows. They are generally formed to include an integral balance system and stops for the exterior and interior surfaces of the sash.
K.D.	Knocked Down - product components that are shipped unassembled, e.g., the frame for a sliding glass door.
keeper	a hardware device into which a window locking latch engages for security. The receiving portion of a lock that interlocks with the lock arm. It’s mounted to the upper sash check rail on a double hung or single hung window and the inside surface of the sash stile on a casement window.
kitchen bay	A small bay window used above counter-height in kitchens -- allows for a wider view and an inside sill for herbs and flowers.
knocked down (kd)	Unassembled window or door unit.
krypton	An inert, colorless gas used instead of air in sealed spaces between panes of glass in insulating glass units to increase insulation. Provides greater insulation than Argon.
laminated glass	two or more lites of glass bonded together with a plastic inner layer.
laminated glass	A type of safety glass comprised of two pieces of glass with a clear vinyl interlay. .
left or right	location information, always outside looking in, that can be used to specify direction, e.g., "the operating sash slides to the right."
lift	A handle or grip installed or routed into the bottom rail of the lower sash of a double hung or single hung window
light	A separately framed piece of glass in a window or door. A traditional double-hung window, for instance, often has several lights divided by muntins in each sash. Such windows are described as six-over-six, eight-over-one, twelve-over-twelve, etc., to indicate the number of lights in each sash. Sometimes spelled 'lite.' A single (monolithic) glass pane or piece.
low e or low-emissivity (low-e) glass	a transparent coating applied to a glass surface to separate long wave (heat) energy and short wave (light) energy. The long wave is reflected back to the heat source. The short wave is allowed to pass through the coating. A special type of glass having a transparent material fused into its surface which acts as a thermal mirror.
low e glass	Low Emissivity glass with a transparent coating which acts as a thermal mirror -- used to increase a window's insulating value, block or increase heat flow, and reduce fading. See Solar Gain and Solar Shield.