The different levels of keying in Master Key Systems have different purposes.

They may be used in many areas such as hotels, factories, hospitals, office complexes, shopping centres, schools and any facilities requiring key control and restricted access.

Generally, most master key systems will be in between Level 1 and Level 5. These levels are extremely important when constructing a system - it is necessary to establish the level of which the system is to be designed.

Key Tree of Master Key System
Key Tree of Master Key System


Level 1: Keyed Alike System (KA)

Keyed alike systems are when a number of locks are required to be operated by the same key.  

Level 2: Master Key System (MK)

Master key systems are used when there are a number of locks each having their own individual key, and also a key that will operate all the locks which are the master key. Using this system, holders of individual keys may open those locks that they are authorised to operate, while those in charge may open all the locks.

Level 3: Grand Master Key System (GMK)

A grand master key system is an extensive system that requires locks to be master keyed in groups, with a master key to operate all locks within its own group but no other group and has a grand master key which will operate all locks in every group.

Thus, people may be authorised to operate individual locks only, all locks in a group, or all locks within the system according to the need of the user.

Level 4: Great Grand Master Key System (GGMK)

The great grand master key system comprises of more than one grand master key system. The key, known as the great grand master key, will work all the grand master keyed areas underneath it.

Level 5: Great Great Grand Master Key System (GGMK)

This type of master key system is extremely complex and not often built. It comprises of more than one great grand master key system. The great great grand master key will operate all locks within the systems below it.



Maison Master Key System

This system can be multi-level and is ideal for residential apartments, offices or facilities with common areas required to be accessed by individual keys.

Each apartment or office has its own exclusive key that will not operate the lock to any other apartment/office and yet at the same time all the individual keys will allow access to main entrance doors and common areas.

Construction Master Keying (CK)

Construction keying is used where it is necessary for contractors to gain entry during construction for a building, but to prevent entry by the same contractors’ key after the building has been occupied or handed over. 

The success of your keying system is in the hands of its designers.

A master key system of any level should always be designed and built to maintain:

  • As much cylinder security as possible,
  • Access control and convenience to the client and staff,
  • Restriction in key duplication for the client. 

For your master key system to function properly you must have precise coding, accurate keys and correct pinning and assembly. John Barnes has been designing, building and installing master key systems for more than 50 years.

We have been creating systems as simple as a few locks, to the complexities of residential apartments, commercial high-rises, entertainment venues, university campuses, and government facilities encompassing many buildings.

We have also created and installed master key systems for medical establishments, prisons, and defence facilities requiring high-level secure area access.