The chief parts of a lock are: the bolt, its essential feature, the selvage, the plate which appears at the edge of the door or drawer, the box, which contains the mechanism including the tumbler, ward, spring, etc., the key-pin, into or around which the key is inserted, the strike, the plate attached opposite the selvage, (often left out as in drawer-locks, but essential in hook-bolt locks, and self-locking locks,) and the escutcheon, the plate around the keyhole.
Locks may be classified: (1) According to their uses, of which there are two types. (a), Fig. 236, For drawers, cupboards, tills, wardrobes, and doors. In these the bolt simply projects at right angles to the selvage into the strike, and resists pressure sidewise of the lock. (b), Fig. 237, For desks, roll-top desks, chests, boxes and sliding doors. In these, the bolt includes a hook device of some kind to resist pressure perpendicular to the selvage. In some locks, the hook or hooks project sidewise from the bolt, in others the bolt engages in hooks or eyes attached to the strike.
Fig. 236. Rim-lock, for Drawer.
1. Bolt. 2. Selvage.
3. Box. 4. Key-pin.
Fig. 237. Mortise-lock, for Box.
(2) According to the method of application, as rim locks, which are fastened on the surface, and mortise locks which are mortised into the edge of a door or drawer or box.
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