Key
A groove in the top of a footing.

Keys
Little fingers of plaster that squeeze through lath.

Keystone
An angular block centered over a door or window in a header or mantle.

Kick-out clause
A clause in a sales contract allowing a seller to accept one buyer's contingent offer then back out without penalty if a second buyer makes a better offer.

Kit home
A structure that contains prefabricated components and is put together by a contractor.

Knee wall
A wall-like structure that supports roof rafters.

Knob-and-tube wiring
An old fashioned wiring system that has been replaced by fuses and circuit breakers.