Mortise locks are generally considered the heaviest duty products in the marketplace. They are typically used in area of high traffic or heavy commercial usage, where greater security is required. A mortise lock is installed in a mortised pocket in the door, with the housing of the lock contained in the door. The cylinder is screwed through the skin of the door directly into the metal lock case, with only the cylinder head and spin ring projecting from the face of the door. The lock case may contain a dead bolt as well as the normal dead latch for added strength and security.
Cylindrical locks are a simpler design installed in two intersecting holes in the door.
The cylinder is contained in the outside knob or lever, away from the surface of the door. Rim locks are mounted to the inside surface of the door, with a cylinder installed on the outside surface in a hole bored through the door. They typically have either a spring latch or dead bolt operation, engaging a strike mounted to the frame around the door. There are several types of dead bolt mechanisms found on rim locks. There are other mechanisms that can be considered under locks, such as hospital latches and exit devices.