A master key system at its simplest form is where each lock in a locking system can be opened with one key, the master key. However, each lock in this system will have its own individual key, and that key can open only that particular door. To better explain this, let’s say that there are 10 doors in this system. Each door will be keyed different meaning that the key for door one can only open door one and no other door. The same for the other nine doors. The master key will be able to open all 10 doors in this system.
Most master key systems are used in commercial applications and can get very large. For example, there could be many systems in a grand master system. The grand master key will be able to open all locks. An example of this type would be in a five story commercial building where each floor will have its own system. The locks on each floor will be keyed different and the master key will be able to open all the locks on that particular floor and no other floor. The grand master keys will be able to open all locks on all five floors.
In the example above you could also group locks on each floor so that each group will be keyed different with one key being able to open all locks in the group, but no other lock. To design very large systems a special computer database program is used to help develop the system and to also keep track of all the locks and keys within it. Needless to say, it takes special skills to develop this type of keying system.
You can’t discuss a master key system without also talking about the lock itself. The maximum size of a particular system is dependent on the lock type and the number of pin chambers in the lock. Generally, the more pin chambers in a lock the larger the system can be. For example, a 7 pin chamber lock will be able to have a larger system than a 6 pin chamber lock. This is due mainly to the number of cuts on the key that can be assigned to any particular system.
Generally the larger the master key system the less secure it is. The most secure lock is one that can be opened by one key and no other. As more keys are able to open the same lock the security will decrease.