A lock puzzle is a type of mechanical puzzle. It consists of a lock 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. Clive Barker's horror novella The Hellbound Heart (later adapted into a movie Hellraiser, followed by numerous original sequels) centered on Lemarchand's box which appears to be such a puzzle box but in fact opens the gates to another dimension when manipulated.
Other lock puzzles stem from the necessity to invent secure locks in the Middle Ages.
Lock puzzles are closely related to puzzle boxes.