What is a Master Key System?

A Master Key System is a hierarchy system where each lock in an organization can be unlocked by an individual ‘change key’, as well as a ‘master key’ that can open them all.

At a very simple level, think of a household of a Mom and Dad with two kids, Johnny and Jenny. Johnny has his own bedroom that Jenny is definitely not allowed in. Jenny has posted a sign that says, “ no boys allowed. Each Johnny and Jenny have access to their own bedrooms, but they are not allowed to enter the others’ territory.

We all know that Mom and Dad’s ‘Master’ bedroom is off limits. But Mom needs to enter Johnny’s room to pick up his stale socks and spray a bottle of febreeze throughout the room. Jenny forgot her ballet shoes that she will need immediately after school for dance class.

Let’s climb the family tree a bit up to Grandma’s house. Grandma and Grandpa spawned more than just Mom and Dad. Mom and Dad have siblings and the siblings also have children. The Siblings, however many there may be, create separate ‘households’, if you will.

What is the difference between the different types of keys?

  • Johnny and Jenny’s rooms represent the ‘Change Keys’ (CK). The Change key is the lowest level of the Master Key System.
  • Mom and Dad’s room represents the ‘Master Key’(MK). This key will operate multiple locks keyed to different change keys. This portion of the system can be broken down in Sub Masters, depending on the complexity of the application. We won’t get into that this time.
  • Grandma holds the ‘Grand Master’ key’ (GMK). Grand-Ma-ster (see what I did there?) is welcome at any one of the households and any of the bedrooms inside. She does share it with Grandpa on occasion.
  • Who holds everything together? Well, God of course. He is the key to the proper functioning of the entire family. God is the ‘Great Grand Master Key’ (GGMK).

Change keys?

Change Key (CK) – This key will only operate one lock or group of locks in a series that are all keyed alike.

How many change keys are possible?

While the Change Key is the lowest level of the Master Key System, there can be several different groups of Change Keys.

Consider Johnny and Jenny’s situation. Johnny has one Change Key and Jenny has another.

We can add more locks to Johnny’s group. He may have his own bathroom, or a closet that all may be keyed the same as his bedroom door lock. Likewise, Jenny also has her own bathroom and maybe even a dance studio her brother is definitely not allowed anywhere near.

The possibilities are endless. Cleaning staff, maintenance, HVAC guys, pest control, babysitter, dog walker, Aunt Georgia. A hospital would have a quite a bit larger system than this family example. It is applicable to apartment buildings, office buildings, factories, horse farms, police and fire stations, restaurants, duplexes, schools, banks, you name it!

So you may be wondering how we can make 2 keys work in one lock …

The first key creates what we call a shearline.

With the use of secondary pins called master pins, we then create an ​alternative shearline(“The shear line is the physical point at which the plug meets the cylinder inside a cylinder-based lock. This point is where components must be properly aligned to allow the plug to rotate and lock or unlock the cylinder.”) ​thus allowing both keys to work the same lock.