LOCKS

There are essentially four types of lock in use: cylinder, sliding, turning and combination.

Cylinder Locks
These consist of a case securely mounted to the door or lid, a bolt which slides in or out and several pegs. The bolt is fashioned with numerous holes into which the pegs fall under their own weight when the lock is closed, thus preventing the bolt from being withdrawn. The lock is opened using a key with a number of pegs corresponding to those in the bolt. As the key is turned the pegs on the key lift up those in the bolt. The pegs on the key also have to have the right length, since if they are too short they will not lift the retaining pegs out, and if they are too long they will hold the bolt in place themselves. This type of lock is generally made of wood, and can be of great size, with keys up to three feet long being required on occasion! In fact, the size of the key is often a sign of prestige and wealth.

Sliding Locks
This type consists of a box within which lies a separate shackle containing a tubular pin and set of springs. The lock is opened by sliding the key into the keyhole. As it goes in it compresses the springs to a level position, allowing the shackle to be be withdrawn. The lock is closed again by simply sliding the shackle back into the box so that the springs are compressed as they pass through the keyhole, then expand once inside the box again. Flanges can be added to the inside of the box so as to catch the springs as they expand and make the lock more difficult for an intruder to pick. The security of the lock depends on the shape and length of the key.

Turning Locks
Turning locks consist of a box holding a bolt in place. A key turned in the lock catches part of the bolt and pushes it in the direction the key is turned. Turned enough times, the key pushes the bolt out of the recess in the doorframe. Turning the key the other way pushes the bolt back in. The key usually has to be turned several times since the bolt has to be fairly long. The problem with this sort of lock is that it is remarkably easy to pick, requiring only a fairly simple tool. Therefore, wards are usually added in and around the keyhole, with the aim of preventing keys of the wrong shape being inserted. In practice, a skeleton key will circumvent this protection and open most locks of this type. To get around this problem, more expensive locks include a bush (metal spike) inside the keyhole, thus preventing a key without a matching notch in the end from being inserted.

Combination Locks
This last type is a rarity not generally known outside of the orient. In principle, they are very similar to a cylinder lock, except that instead of using a key a number of symbols have to be aligned in a particular sequence. The advantage of such a lock is that it cannot be picked, as it has no keyhole. The disadvantage is that, given enough time, even a completely unskilled thief can open it by finding the combination!