A master key system is a set of locks that are keyed so that they each may have an individual key, called a pass key, yet all are opened by an additional, special key called a master key. These locks would be described as keyed different and master keyed.

Within a master key system, groups of locks can be keyed alike, so that the same key operates all locks in the group, plus all locks in the group are operated by the master key. These locks would be described as keyed alike and master keyed.

Under the master, groups of locks can be keyed different, keyed to a submaster, and keyed to the master. For example, you might have three buildings. Each building has six locks keyed differently and a submaster key that operates all the locks within a single building. The master key opens all the locks in all three buidlings, but the submaster from one building will not open any lock in either of the other two buildings.

A grand master key might be necessary if a property manager is responsible for groups of buildings, for example. Each group of buildings would be under a seperate master key; each building would have a submaster key; and overall would be the grand master key that would open everything.

The weakness of a master key system is in the key control. If the wrong person gets a copy of the grand master key, every lock in the system may have to be changed. For my article on Key Control, please visit:

http://hubpages.com/hub/Key-Control-is-Accomplished-not-Bought

The way a master key system is laid out determines the ability that each individual key holder may have to operate any given lock. Therefore it is best to have a clear idea of who needs to get in where before you start.

If your master key system is going to be part of new construction, use the door numbers from the architect's hardware schedule to identify the doors. If this is an existing facility, you can assign names or numbers to the doors as you see fit. the point of this is to be able to match up a key with a door into to future so that you will be able to look at your keying schedule and identify what keys open which door.

Typically locksmiths number keys in a master key system similar to this:

• Grand Master: A
• Master: AA
• Submaster: AAA
• Pass or Change Key: AAA1

If there are no submasters and no grand master, the master key would simply be numbered "A" and the pass keys "A1", "A2", etc.

Once you have identified your doors and settled on a key numbering system, you are ready to design your master key system. At this stage a spread sheet as shown below can be a very helpful graphic organizer for your system.

In the above partial spreadsheet, key numbers are input across the top and door numbers are indicated down the left side. We see that the master, key number "A", opens all doors in the system. The "AA" submaster will open all doors except the Janitor's Closet and the Electrical Room. The "AB" submaster opens only the Janitors Closet, the Lab, and the Electrical Room. Key number "AA1" opens only the Office Entrance, etc.

Once you have added all doors and keys to the spreadsheet you are ready to speak intelligently with your locksmith about how you need your system to work.

If you have any questions, please comment and I will respond.