Lock

Insert the keys in the lock and try to turn them - it will only be possible with one of them. You can watch how the mechanism that we use every day works. The main part of standard locks is the cylindrical plug. It is a cylinder with a hole for the key, which contains several key pins and blocking pins. After inserting the correct key the pins will move to a position where the cylinder of the plug may freely rotate. If the wrong key is used the cylinder won't turn.