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A bypass occurs when a lock is compromised without affecting the integrity of the lock cylinder. Generally, the bolt or actuator are targeted, though in some methods a knob or handle on the rear of a door is manipulated to allow entry. Bypass takes many forms, and can be either non-destructive or destructive depending on the technique used.

Bypass may also be used as a generic term for any technique used to compromise a lock.

Methods of Bypass

There are few generic methods of bypass for lock cylinders; techniques are specific to design or installation flaws present in certain locks.

Padlock Shimming
Padlock shimming is perhaps the most ubiquitous method of bypass. It involves taking a small piece of metal and separating the locking bolt from the shackle in a padlock. Many low to medium security padlocks are vulnerable to this technique. Shims are available commercially, but can be made quickly with aluminum cans or, surprisingly, sufficiently strong paper.
Handcuff Shimming
Handcuffs may be shimmed in a similar manner to padlocks. It involves using a small piece of metal and directly retracting the ratchet or interefering with the ratchet's ability to detain the pawl arm. This bypasses the lock mechanism entirely and is the reason that most handcuffs have a double lock mechanism.
Lock Actuator Attacks
Flaws in the design and placement of the locking actuator for the cylinder may allow a bypass tool to retract the locking bolt without the proper key inserted, or even internal components being in the proper positions. Various lock manufacturers have suffered from this vulnerability in the past.
Locking Bolt Attacks
Flaws in the design or installation of the locking bolt may allow the bolt to be retracted without using the correct key or picking the lock cylinder. The classic credit-card opening of doors (known as loiding) and the use of slim jims on cars are two popular examples.
Magnetic Manipulation
Locks and locking systems that make use of solenoids, electronic relays or components made of ferrous materials can be vulnerable to magnetic manipulation.

See also

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