The following terms define Building and Machine Parts
keystone: central, uppermost stone of arch.
keystone joist: joist made of reinforced concrete with sloping sides and tip wider than bottom keyway groove or slot cut in shaft or hub to hold key.
king post: vertical member between apex arid base of triangular roof framework
knob: round handle.
knuckle joint: joint permitting movement between parts in one plane only L angled support beam, brace, or bracket.