Skeleton key is a specialised type of key designed to open numerous locks, most commonly lever tumbler locks. It achieves this utility by having minimal mechanical features that correspond to a specific lock's complexity, primarily by bypassing the wards—obstructions within a lock that prevent incorrect keys from turning. The design of the skeleton key involves a simplified bit, or blade, which is shaped to pass through the wards without specific alignment. This generic form allows it to operate multiple locks within a similar configuration.
Such keys are historical artifacts in locksmithing but continue to find relevance in applications where a single key is needed to operate multiple locks, such as in older residential buildings or certain institutional settings like prisons and schools. Their ability to open multiple locks does not extend to more secure locking mechanisms, such as pin tumbler locks, which require more precise key cuts corresponding to the lock’s pin heights. In contemporary contexts, skeleton keys often symbolise universal access and are frequently employed in popular culture to represent the unlocking of hidden or mystical treasures. Their enduring design reflects an essential understanding of mechanical lock engineering before the advent of high-security lock systems.