The Union 2277 102mm 3 Lever Mortice Sashlock Satin Chrome is for wooden doors hinged on the left or the right, requiring key operation & a latchbolt. The lock is locked or unlocked by a key from either side. The steel case is silver enamel painted. The lock case (except 50mm case) is pierced to accept bolt through door furniture & suitable for use with unsprung lever handles. In general the 3 lever 2277 sashlock will be used for internal doors only, it is not recommended for external doors as it has no insurance rating. The 2277 sashlock will usually be used on cupboards, . ..