Keeper - The metal latch plate in a door frame into which a doorknob plunger latches.
Keyless - A plastic or porcelain light fixture that operates by a pull string; generally found in the basement, crawl space, and attic areas.
Key way - A slot formed and poured on a footer or in a foundation wall when another wall will be installed at the slot location, giving additional strength to the joint/meeting point.
Kiln-dried Lumber - Lumber that has been kiln dried often to a moisture content of 6 to 12 percent; common varieties of softwood lumber, such as framing lumber are dried to a somewhat higher moisture content.
Kilowatt (kW) - One thousand watts; a kilowatt hour is the base unit used in measuring electrical consumption.
King Stud - The vertical "2 X's" frame lumber (left and right) of a window or door opening, and runs continuously from the bottom sole plate to the top plate.
Knot - In lumber, the portion of a branch or limb of a tree that appears on the edge or face of the piece.