UNION C-Series 3M51 Detainer Clutch LockUnion C Series (formerly known as Chubb) 3M50 5 Detainer Clutch Mortice lock Projecting stump on the forend engages into locking plate to prevent door being lifted from the frame in the locked position Suitable for timber sliding doors requiring automatic closing action Suitable for doors up to 50mm thick UK Manufactured with 10 Year Guarantee EN1634 1 use on 60 min timber fire doors Formerly known as Chubb