The Atlantic Elite Range consists of 3 Lever Deadlocks, Euro Deadlocks and 5 Lever Deadlocks British Standard BS3621, all in 2.5? and 3?. A Mortice Deadlock can only be operated with a key. Deadlocks have a single bolt that secures into the door and offers extra strength. There is no latch, therefore handles arent required to release the door. A 3 lever lock has 3 levers that move into position when the key is entered and turned in the lock, whereas a 5 lever lock has 5 levers offering extra security. 5 Lever locks are usually fitted on external entrance doors. 3 lever locks are often fitted internally, perhaps between a home and garage. A Euro Deadlock is a deadlock where the locks is operated by the Euro Cylinder with one full turn of the key.