These consist of a latch operated from the outside by a key, and from the inside by a thumb knob or slide. A stop is always provided for holding back the latch when desired. They are made both rim and mortise, but the rim locks are generally used for the reason that they do not weaken the door and are more easily applied.
Night latches are very extensively used on office doors, club house doors and the rear outside doors of residences. They are always used in addition to an ordinary knob lock and latch. As they are used principally to give greater security, it is hardly worth while to-put on a tumbler lock, hence nearly all the night latches now used have cylinder escutcheons. For ordinary purposes rim night latches-are finished in black japan, but bronze metal cases are made for rooms where an ornamental finish is desired. The better grade of rim locks have the striking plates and front plate of lock extended so-that they may be screwed to the jamb and edge of the door, thus necessitating breaking of the woodwork to force the door. The Yale & Towne Manufacturing Co. have recently introduced an oxidized copper rim lock which is made so that no screws are exposed when the door is closed, the case being attached to the door by an interlocking back plate screwed to the door and by two screws in the edge of the door. Rim night latches may be used on either right or left hand doors, but if the door opens outward a reverse bevel is required.