The union strongbolt bs 5 lever mortice sash lock 81mm is ideal for timber doors hinged on the left or right and they are suitable for doors up to 54mm thick the deadbolt is locked or unlocked by the key from either side with the 20mm deadbolt for secure positive deadlocking and additional resistance against attack features an anti pick anti saw and anti drill security chamfered bolt design that increases the performance of the lock under side load testing the chamfer of the bolt also makes