1. Master Keying
2. Master Keying System

Master keying refers to the keying procedure that makes one lock work with two or more key cut combinations. The master key will be able to open all locks in a complex, and the other key (the tenant key) will only be able to open one lock in the complex. The right combination of bottom pins and master pins will produce a shear line for both keys. A master key system allows two or more keys to open one lock. To make a master key system, you need locks and keys that are the same make and model, and a way to rekey those locks. The basic pin tumbler master locks use a master wafer/pin in between the key pin and the driver pin. Measure the five cuts on the original key and the master key using the scale on the key gauge. Master Key Contact Events Folder: Resources. Books Folder: Book a Time. Coaching Invite Enroll Now Unlock Your Original Design.

The super of our apartment building is always going into everyone's apartment when something needs to be fixed. There must be a hundred apartments, but he only carries one key around with him. How does he get into all those apartments with the same key?

Master Keying

Although locks come in all shapes and sizes, with many innovative design variations, most locks are based on fairly similar concepts. The most common lock design is the cylinder lock. In this design, the key turns a cylinder, or plug, which turns an attached cam. When the plug is turned one way, the cam pulls in on the bolt and the door can open. When the plug turns the other way, the cam releases the bolt and a spring snaps it into place so the door cannot open.

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The key your 'super' is using is called a master key. To understand how master keys work, you first have to have a basic idea of how locks and keys work.

Inside a cylinder lock, there is a sort of puzzle, which only the correct key can solve. The main variation in lock designs is the nature of this puzzle. One of the most common puzzles is the pin-and-tumbler design.

Check out the next page to learn more about this lock design.

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The main components in the pin-and-tumbler design are a series of small pins of varying length. The pins are divided up into pairs. Each pair rests in a shaft running through the central cylinder plug and into the housing around the plug. Springs at the top of the shafts keep the pin pairs in position in the plug.

When no key is inserted, the bottom pin in each pair is completely inside the plug, while the upper pin is halfway in the plug and halfway in the housing. The position of the upper pins keeps the plug from turning -- the pins bind the plug to the housing.

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When you insert a key, the series of notches in the key push the pin pairs up to different levels. The incorrect key will push the pins so that most of the top pins are still partly in the plug and partly in the housing. The correct key will push each pin pair up just enough so that the point where the two pins come together lines up perfectly with the space where the cylinder and the housing come together -- this point is called the shear line.

Some locks are designed to work with two different keys. The change key will open only that specific lock, while the master key will open that lock and several others in a group. In these locks, a few of the pin pairs are separated by a third pin. This third pin is called a master wafer or spacer.

When three pins are combined in a shaft, there are two ways to position the pins so they open the lock. The change key might raise the pins so that the shear line is just above the top of the master wafer, while the master key might raise the pins so the shear line is at the bottom of the master wafer. In both cases, there is a gap at the shear line and the key is able to turn.

In this lock design, the lowest pin is the same length in each lock in the group, but the master wafer varies in length. This lets the person with the master key access any lock in the group, while someone with a change key can open only his or her own lock.

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One cool thing about pin-and-tumbler locks is that you can re-configure them to fit an existing key (provided that the key is for the same lock design). The advantages of this are obvious: You can add new locks to your home or business without attaching a bunch of new keys to your key ring.

To make a new key for an existing lock, you cut a series of notches in the key so that it raises each of the upper pins just above the shear line. Essentially, you cut a pattern in the metal that matches the pattern of the pins in the lock. To change a lock so that it fits an existing key, you simply work in the opposite direction: You change the pattern of the pins in the lock so that it matches the pattern of notches in the key. If the lock is designed with a universal keying system, any locksmith can re-key the lock in no time. You can also get locks re-keyed at most hardware stores.

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In this basic six-pin lock set, you can see how this re-keying works. When you open up the shafts in the cylinder and empty them out, you have six springs and 12 tiny pins. All of the upper pins are exactly the same size. The remaining six pins (the lower pins) will be of various lengths to match up with the notches on the key.

The process of re-keying a lock is very simple. The locksmith removes all of the pins from the cylinder. Then, drawing from a collection of replacement pins of various sizes, the locksmith selects new lower pins that fit perfectly between the notches of the key and the shear line. This way, when you insert the new key, the lower pins will push all the upper pins just above the shear line, allowing the cylinder to turn freely. (This process may vary depending on the particular design of the lock.)

It doesn't matter how long the upper pins are (since they all rest above the shear line when the key is inserted), so the locksmith simply re-inserts the six original upper pins that came with the lock. And that's all there is to re-keying. The entire process takes only a few minutes.

Master keys are an interesting technology somewhat related to lock picking (because they're means of getting past locks without the main key).

Some locks are designed to work with two different keys. The change key will open only that specific lock, while the master key will open that lock and several others in a group. In these locks, a few of the pin pairs are separated by a third pin called a master wafer or spacer.

When three pins are combined in a shaft, there are two ways to position the pins so they open the lock. The change key might raise the pins so that the shear line is just above the top of the master wafer, while the master key would raise the pins so the shear line is at the bottom of the master wafer. In both cases, there is a gap at the shear line and the key is able to turn.

In this lock design, the lowest pin would be the same length in each lock in the group, but the master wafer would vary in length. This lets one person, say a building manager, access many different locks, while each individual key-holder can open only his or her own lock.

Master Keying System

In the next section, we'll look more closely at the differences between lock picking by locksmiths and illegal lock picking.