From the Renaissance, locks comprised a rectangular casing, which contained one or several bolts operated from the interior by a key and from the exterior by a sliding knob.

It was in this era that first mention was made of master keys. Accounts of the King's residences tell us that in 1547, Henri II had fitted to the door of Diane de Poitiers, "three large locks, which were opened by a key held by the King and which fitted anywhere".