Master key

=Master Keying=

Master keying is a keying system in which more than one key can operate a lock or group of locks. Master keying is commonly used to restrict or allow access to a group of locks in a facility based on a user's access level. Various types of master keying exist depending on the type of lock and the number of access levels required. The use of master keying can have a dramatic effect on the number of real key differs and resistance to various forms of covert entry, such as lockpicking and impressioning.

Master Key Lock Designs
The type of lock will determine what master keying schemes are available. Each lock design has a different method of providing master keying either by adding components, modifying keys, or both.


 * Combination
 * Traditional rotary combination locks can have have multiple true gates per wheel, allowing various combinations to be used. The majority of combination locks do not allow master keying without the addition of an auxillary override lock. Electronic combination locks can store a database of valid combinations for different users.


 * Disc-detainer
 * Widened or additional true gates on the discs themselves can allow master keying. The high number of key differs in most disc-detainer locks minimizes the threat of key interchange in most systems.


 * Lever
 * Various modifications to the levers themselves can allow master keying but most have an adverse effect on security. The majority of real-world lever locks that need to provide master keying do so by providing two keyholes with two sets of levers, or two keyholes with a single set of levers, each lever having two contact points.


 * Pin-tumbler
 * Adding additional, smaller pins between the top and bottom pins of each pin tumbler stack allows for additional shear lines to be created. Pin-tumblers provide one of the most versatile master keying solutions.


 * Wafer
 * Wafers are modified to have two contact points. The normal (change) key will pick up one set of contact points and master keys the other.


 * Warded
 * Warded keys are modified to fit through different warding designs; the locks themselves are rarely modified.

Master Keying Schemes

 * Interchangeable Cores
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 * Maison Keying
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 * Master Rings
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 * Partial Position Progression
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 * Rotating Constant Progression System
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 * Sectional/Multiplex Keyways
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 * Total Position Progression
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