Lock puzzle

Lock puzzles are puzzles usually in the form of locks for a door, but with unusual or hidden mechanics. Such locks are sometimes called trick-locks, because opening them is like performing a magic trick. A matching key may or may not be used in this trick.

Lock puzzles have a long history. Chinese jewelry boxes often contain trick-locks and hidden drawers. An example of such a box is an integral part of the plot of the movie Shanghai Knights.

Other lock puzzles stem from the necessity to invent secure locks in the Middle Ages.