Skeleton key

A padlock skeleton key that can open any lock with this keyhole (right), compared to a normal key that can open only the lock for which it was made (left).

A skeleton key (also known as a passkey) is a type of master key in which the serrated edge has been filed down so that it can open numerous locks,^[1] most commonly the warded lock. The term derives from the fact that the key has been reduced to its essential parts.^[1]

In a broader sense the term can be used synonymously with master key to refer to any key, keycard or other device capable of opening a variety of locks.

In US English usage, 'skeleton key' is also occasionally used to mean a standard lever lock key. It is sometimes misapplied to refer to any antique key.

Master keys

A skeleton key is a key that has been filed or cut to create a master that can be used to unlock a variety of warded locks each with a different configuration of wards. This can usually be done by removing most of the centre of the key, allowing it to pass by the wards without interference, operating the lock. To counteract the illicit creation of such keys, locksmiths can put wards not just in the centre but on the outside as well, making the creation of a skeleton key more difficult.

Lever lock skeleton keys are used in a lock with usually three or five levers and a set of wards that come into contact with the bit of the key only on the sides – the top is for pushing the levers to their correct heights while the warded section of the key just has to pass uninterrupted to allow the key to rotate fully. A master key system of lever locks has the same lever heights in all locks. Each door will have different wards and can only be opened by the correctly warded key or the master key. A skeleton key has the warded section of the key removed so that it opens all the doors of a system. Some applications, such as a building with multiple entrance doors, have numerous locks that are keyed alike; one key will open every door. A keyed-alike system is different to a master key system as none of the locks have a key that can open only that lock.

Skeleton keys have often been associated with attempts to defeat locks for illicit purposes, to release handcuffs for example, and standard keys have been filed down for that purpose. Legitimate skeleton or master keys are used in many modern contexts where lock operation is required and the original key has been lost or is not available. In hotels without electronic locks, skeleton keys are used by housekeeping services to enter the rooms.

Lever lock keys

A lever lock key.

In US English usage, 'skeleton key' is occasionally used to mean a standard lever lock key.This usage perhaps stems from such keys' resemblance to a skeletal figure, with the circle at top circumscribing the triangle at one-third the vertical length, resembling a stylized skull.

These keys were common in both cabinetry and door locks in early Colonial America and remained in common usage within the United States through the 1940s, giving way after World War II to the pin tumbler lock. Most keys of this type and their locks were formed of brass, although pewter was sometimes used. They were commonly available at hardware and other stores. Today, lever lock keys are associated with fine cabinetry.

See also

• Master key
• Bump key, a similar universal key / pick used on pin-tumbler locks.

References

Locksmithing & Lock picking
Topics	Electric strike Key control Key relevance Lock bumping Lock picking Lockout-tagout Maison key system Rekeying Single-point locking Three-point locking
Components	Bitting Bolt stump Break Interchangeable core Key blank Key code Keyhole Lockset Shear line Split pin
Key types	Berlin key Bump key Change key Master key Skeleton key Smart key Tubular key Transponder key
Mechanical Locks	Bored cylindrical lock Bramah lock Cylinder lock Disc tumbler lock Key retainer Lever tumbler lock (Chubb detector lock) Magnetic-coded lock Magnetic keyed lock Mortise lock Padlock Combination lock Rotary combination lock Time-delay combination locks Pin tumbler lock (snib) Protector lock Relocking device Time lock Tubular pin tumbler lock Warded lock Wafer tumbler lock
Electronic Locks	Electromagnetic lock Electronic lock Electric strike Magnetic-coded lock Keycard lock Electronic/digital-cylinder pin tumbler lock
Specific lock types	Bicycle lock Chamber lock Child safety lock Dead bolt Keycard lock Kensington Security Slot Luggage lock Power door locks The Club TSA lock
Tools	Lockpick Slim Jim Snap gun Tubular lock pick
Related	Bolt cutter Door chain Exit control lock Famous locksmiths Interlock (engineering) Keychain Key (engineering) Lock manufacturers Lock puzzle Lock snapping Locksport Two-man rule
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