How to Lay Out a Master Key System Schedule
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.
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.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
How should I go about developing the bitting codes to be used in my system?
These days locksmiths use master keying software to create master key systems in a flash, and it is a good way because the software seems to never make any errors. And errors are easy to make.
When I made master key systems using a paper and pencil, I started with the master key bitting. The trick is to always be conscious of the incidental bittings one creates during the process. For example, say you make a very small master key system:
Master Key A: 52531
Key number A1: 54215
Key number A2: 55967
In this small system, if I were to add bitting 55537, it would also open the lock keyed to A2. That's called cross keying, and it results from individual digits within the bitting matching either the master key or an operating key. In this case, one could change the bitting to 55533 and solve the problem.
I used to do fairly well avoiding cross keying by keeping one digit the same as the master and then adding a certain number to each other digit to come up with the next change. For example, in the series above, the next change would be 56519. In some systems, having the 1 and the 9 next to each other might not work out because they are too close together; when you cut the 9 it cuts away part of where the 1 was, and now it ends up being some nonexistent bitting like 2.4 or so.
Also, one wants to avoid monotone (i.e. 55555) or ramp (i.e. 54321) bittings that are super easy to pick; also each digit of every operating key should vary from the corresponding digit in the master key by at least 2 so as to avoid the dreaded #1 master wafer that tends to drift out of place as the lock becomes worn over time.Helpful 6
1) Which codes make a good master key? What is your preference? 2) Do you have a good reference for the rules of binning? 3) I am finding it difficult to find well-made DND key blanks. It seems that even Ilco keys vary depending on who they farm the manufacturing to. I have noted that there is a lot of up and down play in the key when in the cylinder due to wider key grooves. Even the brass seems of cheaper quality than the ones they made in the past.
As with all keys one originates, avoid 'ramp' (like 123456) and monotone (like 222222) bittings and bittings that have extreme adjacent depths (like 190829). Grand master keys may be thinner than operating keys if there are several different keyways in the master key system, so in that case try to avoid the deepest cuts so that the key is more durable.
Manufacturer's original key blanks and cylinders are usually much better quality. Dorma Kaba Ilco is an aftermarket cylinder and key blank company that produces good quality products, but if you want to be able to use the pin size your keying kit tells you to use, you will need to use original cylinders and key blanks.
Then instead of a lot of trial-and-error guesswork, it's just a matter of putting the right pin in the right hole.
Manufacturer's original key blanks are also available pre-stamped "Do Not Duplicate," or you can buy your own hand stamp and stamp them yourself. Most if not all lock companies have gone to nickel-silver blanks instead of brass because nickel-silver is so much more durable.Helpful 1
How do you grand master and master a lock with a tenant key?
A basic of master keying a standard pin tumbler cylinder is to add extra top pins to one or more pin stacks to create additional combinations. Each additional combination that is created will permit another key to work the lock. Simply put, if you add one top pin to one pin stack, it will create one new combination. If you add two, it will create two. If, however, you add one pin to one stack and one pin to a second stack, now there are twelve keys that will work this lock. This makes grand master keying possible, and it also makes it difficult to achieve securely.