Keystone
Angular block, in a header or mantle, centered over a door or window or at the top of a masonry arch.

Kick-out Clause
Sales contract clause, which allows a seller to accept a contingent offer and then back out to accept a second and better offer without penalty.

Kicker
Payment required by a mortgage in addition to normal principal and interest. Also called an equity kicker or participation loan, it allows the mortgagee to participate in income from the mortgagor.

Kiosk
An independent stand from which merchandise is sold, often placed in the common area of a shopping center.

Kit Home
Structure containing prefabricated parts, which is assembled by a contractor.

Kitchenette
Tiny kitchen area that is often built into the end of another room such as a room in an efficiency apartment.