A warded lock (also called a ward lock) is a type of

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that uses a set of obstructions, or ''wards'', to prevent the lock from opening unless the correct key is inserted. The correct key has notches or slots corresponding to the obstructions in the lock, allowing it to rotate freely inside the lock.

History

The warded lock is one of the oldest lock designs, which can be found as far back as

ancient China The earliest known written records of the history of China date from as early as 1250 BC, from the Shang dynasty (c. 1600–1046 BC), during the reign of king Wu Ding. Ancient historical texts such as the '' Book of Documents'' (early chapte ...

and

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. During the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...

they were used prolifically on monasteries where, because money and time were available, their complexity grew. Warded locks are still in use today in the UK and Ireland for low-security applications, and on

heritage sites A national heritage site is a heritage site having a value that has been registered by a governmental agency as being of national importance to the cultural heritage or history of that country. Usually such sites are listed in a heritage regist ...

such as ancient monuments and churches to preserve original features, with primary security being provided by other means such as a lever lock mechanism installed in addition.

Design

In a basic warded lock, a set of obstructions, often consisting of concentric plates protruding outwards, blocks the rotation of a key not designed for that lock. Warded locks may have one simple ward, or many intricate wards with bends and complex protrusions; the principle remains the same. Unless the notches or slots in the key correspond to the wards in the lock, the key will strike an obstruction and will not turn. Additionally, a series of grooves on either side of the key's blade may limit the type of lock the key can slide into. As the key slides into the lock through the keyway, the wards align with the grooves in the key's profile to allow or deny entry into the lock

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

. Although this is not commonly recognized when discussing warded locks, it is more applicable to current

locksmithing Locksmithing is the science and art of making and defeating locks. Locksmithing is a traditional trade and in many countries requires completion of an apprenticeship. The level of formal education legally required varies from country to country ...

applications such as pin-tumbler or wafer-tumbler locks. In double-sided locksets (meaning locksets where the key can be inserted from either side of the door) the centre of the key shaft is solid and protrudes past the end of the

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which slots into a hole on the opposite side of the lock. Double-sided ward locks nearly always have perfectly symmetrical bits. For single-sided locks, a cylindrical post is typically located in the center of the lock. Its purpose is to provide a point of leverage and pivot for rotating the key, and to help correctly align the key with the wards. The key has a corresponding hole which fits over the post. When the correct key is inserted, it will clear the wards and rotate about the center post. The key may then strike a lever, activating a latch or sliding bolt, or it may itself push against the latch or bolt. In a double acting lever lock, the key may additionally push against a spring-loaded lever which holds the sliding bolt in place.

Vulnerabilities

Due to the design of the lock, a well designed

skeleton key A skeleton key (also known as a passkey) is a type of master Lock (security device), key in which the serrated edge has been removed in such a way that it can open numerous Lock and key, locks, most commonly the warded lock. The term derives fr ...

can be made to bypass the wards. For this reason, warded lock mechanisms are generally used in low-security applications. There are also a very limited number of unique keys that can be created, so many keys will be able to open other doors that they were not designed to open. The invention of the

lever tumbler lock A lever tumbler lock is a type of lock that uses a set of levers to prevent the bolt from moving in the lock. In the simplest form of these, lifting the tumbler above a certain height will allow the bolt to slide past. The number of levers may va ...

solves this problem, as each lever is required to be lifted to a certain height in order to operate the locking mechanism.

References

{{Locksmithing Locks (security device)

History

Design

Vulnerabilities

See also

References