How to Lay Out a Master Key System Schedule

Updated on October 22, 2016

What is a Master Key System?

A master key system is a set of locks that are keyed so that they each may have an individual key, called a passkey, 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 buildings, 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 separate 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.

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.

Identify the Doors

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 in the future so that you will be able to look at your keying schedule and identify what keys open which door.

Key with Visual Key Control
Key with Visual Key Control | Source

Identify the Keys

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.

At right is a photo of a key that is part of a master key system. Notice the number: "2818AA"

This would indicate to me that the system has a master key numbered "A", submaster keys numbered "AA", "AB", etc., and pass keys numbered "1AA", "2AA", etc.

Submaster keys are often created to match the hierarchy of the users and/or the structure of the building. For example, a building might have five floors with a different office tenant or department on each floor. In this case one might assign one submaster key to each floor.

Sometimes submaster keys are created for different users. For example, maintenance people may have a submaster key that accesses utility and machine closets and building entrances only.

Once you have identified your doors and settled on a key numbering system and how you are going to organize it 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.


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    • Tom Rubenoff profile image

      Tom Rubenoff 15 months ago from United States

      Hi Mac! Number of possible changes varies widely between pinning technologies and manufacturers. Also there's a big difference between possible changes and usable changes. That's why most locksmiths use master keying software these days.

    • Tom Rubenoff profile image

      Tom Rubenoff 15 months ago from United States

      Hi Vremner, sorry I didn't see your comment before. Thanks very much. In my career I found the biggest obstacle to getting a master key system right was getting the customer to understand the concept. This article is my attempt to address that.

    • profile image

      mac0070 15 months ago

      Hi, Can you tell me How many possible change keys will be generated under a single master key only system ? (just a master key no sub masters ) Thanks Mac

    • profile image

      vremner 15 months ago

      Really great hub! I have been using this techique a lot and it seems to be pretty good. When rekeying an office or similar you basically can do both ways - from bottom to top and from top to bottom. In my opinion, you hadnt covered all area to people to choose from but boy this is a good tipp. You are almost selling our knowledge

    • Tom Rubenoff profile image

      Tom Rubenoff 17 months ago from United States

      If you are talking about a relatively small system, you could create it without the use of a computer.

      Create your master key and sub-master key bittings first. For example:

      Master key: "A"


      Sub-master key: "AA"


      Now create your first change key, "AA1":


      You can see that the cylinder keyed to "AA1" can be easily keyed to all three keys. The pin stacks would look like this:

      1 4 1 1 6 4

      3 x 7 2 2 2

      2 x x 3 x x

      Under the sub-master "AA" all keys will have a #4 cut at the second and sixth positions. All cylinder not under the "AA" sub-master will not have a #4 cut in either of these positions, nor will that have a #2 cut in the sixth position to ensure that no other key in the system will open these cylinders you have keyed to three levels.

      Alternatively you could create a sub-master using your software by using sectional keyways. For example, using Sargent L series keyways, you could use an LD keyway for your master key and LB keyway for your sub-master key, use LB keyway for your sub-master-keyed cylinders, and LA keyway for all the other cylinders in the system. Your LB keyway sub-master will only pass the LB keyway cylinders and your LA change keys will not pass them. The LD keyway master key will pass everything. You still need to avoid cross keying, but at least folks won't be able to try their keys in the LB keyway cylinders unless they have them re-cut on an LB, LD, or LN keyway blank.

      I hope you find this helpful.

    • profile image

      David E. Gust 17 months ago

      How do you key 1 cylinder to 3 keys on a standard cylinder? How can I do it in the field without using a huge computer program? My program does not allow me to input the sub master that some clients want.

    • Tom Rubenoff profile image

      Tom Rubenoff 5 years ago from United States

      Sure. What did you have in mind?

    • profile image

      Scott 5 years ago

      I manage some buildings and would like to have my own 4 level key code system. Can you help get started.

    • Tom Rubenoff profile image

      Tom Rubenoff 5 years ago from United States

      Thank you!

    • louromano profile image

      louromano 5 years ago

      Excellent hub. good info

    • Tom Rubenoff profile image

      Tom Rubenoff 6 years ago from United States

      If I keyed locks to work with the grandmaster and a pass key only, the grandmaster key being "A", I would number those pass keys A1, A2, A3, etc. This is typical key numbering used for mechanical closets, storerooms and utility closets accessible to maintenance staff only.

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      Wayne 6 years ago

      If you have a system (A Grand Master, AA thru AE masters )and need to add keys under the master only (A1-A5) would you simply create numbers for another master, not cut it and then cut keys that would be under that master and label them A1-A5?

    • Tom Rubenoff profile image

      Tom Rubenoff 6 years ago from United States

      Yes, I have, but my general experience is that building owners and facility managers may be unlikely to be able to give you the information you really need because they lack the expertise. Often, for example, they want everyone's key to work in the front door - an easy thing to accomplish, but not really advisable in a building with more than three changes in it.

      The only questions building owners/managers are usually capable of answering concern who should be able to open what. Therefore the most practical way to proceed would be to ask them to list their doors and the people who need to get into them when they are locked. From that information, the locksmith can begin to create a keying schedule.

      For information about door swings and lock and cylinder types, nothing really can take the place of a site survey.

      All the best,


    • profile image

      drew 6 years ago

      Can you tell me if you have ever run across a questionaire for use in helping clients develop a keying schedule?

      I would love to be able to leave something with a building owner so they can answer simple yes/no type questions to aid in distilling their keying needs.