Suitable for night use in high security locations such as offices and industrial premises. For day use, the lock should be supplemented by a more suitable lock. EL558 is a Hi-O device, which means it can communicate with other Hi-O locks for coordination, synchronization, behaviour monitoring and other high tech needs. The Hi-O system is built in the lock instead of a centralized database, which makes it more secure. When installing EL558 in a system without Hi-O capabilities, a controller (DAC564) is needed to mediate between the lock and the outside world. EL558 have latch bolt and hookbolt.