This chapter discusses the elements that are mechanical in nature. Mechanical locks and latches require electrical power and can therefore be installed in any installation. The cylinder lockset is installed in a round hole cut into the door at the doorknob. The mortise lockset is a different design from the basic cylinder lock. The combination lockset uses a numeric keypad requiring the numbers to be pressed in a certain order to release the latch. Many key manufacturers now have a policy that only certified locksmiths can re-cut keys for their locks. Some lock vendors also provide, with their locks and keys, software programs for lock and key control. Doors have mechanical hardware to close and latch the door and the hardware has locks and keys for security. Modern hinged doors have a “latch” and a “strike.” The latch and strike work together to hold the door closed.