Master keys are something that many people seem to be fascinated with. The fascination, I believe, is due to the confusing nature of the device. How is one key, opening two doors, but another key that is opening one of those doors is not opening the other? Is it the key that is special? Is it the internal mechanics of the lock? Well, I must warn you that there is some math involved in these answers. At the lowest level of comprehension, it is addition and subtraction, and at the highest level of understanding (at least what is expressed here), it is exponents. It is nothing scary. After reading this piece, you should be able to understand any master key system, varying from the most straightforward version to the most complex. With the basic understanding, one should be able to extrapolate potential additions to the system’s security.
In order of least access to most access:
Change Key – This key is also referred to as a sub-master key. It will open one lock and only locks that are the same. The lock that the change key opens will also open with the use of the master key, and any key above that rank.
Master Key – Without a master key, there is only one key for a lock. This is the necessary key to change a simple lock into a master keyed lock. In some systems, this will be the highest-ranking key. In the trade, a master key may be shortened to ‘MK.’
Grand Master Key – A grand master key is used to access multiple master key systems. This key will open every master system under it, and the subsequent change keys under those systems. In the trade, a master key may be shortened to ‘GMK.’
Great Grand Master Key – The great grand master key will open all the grand master key systems under it, the master key systems under those, and the change keys under those. Theoretically, this trend can continue until the locks become too complicated to function. There could be grandmaster keys prefaced with great great great great, etc. etc.
Most master key systems work off of a basic pin tumbler lock. A quick review of how a basic pin tumbler lock will work: To open a lock, a pin stack consisting of a driver pin and a key pin must be elevated so that the two rest on opposite sides of the shear line. A key lifts key pins within a lock. These key pins are all different sizes. The driver pins will be a universal size. Therefore, the key needs to have the right set of grooves to lift the key pins to the correct height. It is an oversimplification, but if you are in Dallas and would like to find out more about the specifics, we are here to assist you. With that understanding, it will be easier to comprehend the addition of a master key system. All that is needed for any standard pin tumbler to be converted for a master key system is to add a master wafer (aka master pin) between a driver and a key pin. A master wafer is virtually a small hockey puck-shaped pin. Once it is in place, the pin stack will have two shear lines. A shear line for a pin stack with a master wafer below or above the line.