Lock cylinder

The lock cylinder is the part of the lock you put your key into: it checks that the key is the right one and, when it is, lets the mechanism turn to draw back or throw the bolt. In Spain almost everyone calls it a “bombín”; catalogues and standards prefer “cilindro”.

Inside it has a fixed body, the housing, and a part that turns, the plug. Between the two there are pins that only line up with the correct key. If the pins do not line up, the plug does not turn.

It is easy to spot: it is the brass or steel part that shows through the escutcheon or the plate on the door, with the keyway in view.

If the key is stiff, you have lost keys or you have just moved into a home that has had previous owners, the sensible thing is to change the cylinder. On the coast salt air takes its toll, so cleaning it in good time makes it last longer.