Deadbolt

The deadbolt is the metal part that comes out of the lock and into the strike plate in the frame to lock the door. On security locks, the main bolt is moved only by the key and cannot be pushed back in from outside.

In everyday Spanish, almost any fastening gets called a pestillo, including the latch that springs in when you close the door. But they are not the same: the latch has a sloping side and gives way if you push it; the deadbolt is square and does not.

That is why a door that has only been pulled shut is held by the latch alone and is easier to open. Turning the key throws the deadbolt and the door is properly locked. More under lock installation.