The yale pm550 5 lever mortice sashlocks offer a high level of security and are suitable for use on external timber doors the deadbolt on the lock is locked or unlocked by key from either side these sash locks also have a 14mm anti saw deadbolt and are pierced to accept bolt through furniture a deadlock has a single deadbolt which is locked or unlocked by means of a key from either side whereas a sashlock has both a deadbolt and a latch which is operated from either side by a lever handle the se