A lock fitting a rectangular shaped cavity in the edge of a door. A round hole in the face of the door receives a spindle to which knobs or levers are attached. If key operated, a second round hole above the first receives the cylinder(s) and thumb turn. Some functions use two cylinders which is not a violation of the codes because the inside knob always operates. Some functions use two cylinders which sometimes is a violation of codes because the inside key projects a dead bolt or locks the inside knob which can only be unlocked by key. (This example of key operation on the inside applies equally to other types of locks and is mentioned under mortise locks only because it originated with them.)