A blueprint for building security is a master key system schematic. Master key for all locks conveys a concept to both allow and limit access to land, much like an architect's design. Any system that provides several "access levels" must be adapted to the unique security demands of the building (or groups of buildings) where it is implemented.

A master key system refers to a collection of locks and the keys that operate them that are connected in a hierarchy with one key at the 'top' that will fit into a large number of locks and a large number of keys at the 'bottom' that may only fit into one lock. The lower the number of master key levels, the more secure the system. Careful planning is required.

A master key is a key that opens many locks connected in some way inside a master key system. An elementary school, for example, may have a master key that opens all classroom doors. But, likewise, each classroom door would be unlocked by a key that only opened that one classroom door.

However, that classroom key may also access a cupboard within the classroom. In other words, if the locks are configured identically, a single key may unlock several locks. For example, if this primary school is part of a district that uses a single master key system for several school buildings, there may be a Great Grand Master key that may be assigned (and cut) to access the school's external doors and all classroom wardrobe door locks.

The top-level key, referred to as the Great Grand Master on the accompanying chart, can unlock all doors in this sample security system; however, each lock has its unique key. Master key systems might be organized along with departmental or other functional groupings to provide supervisory or emergency access. The next level, known as the Grand Master key, can only access specific doors. The initial level, or Change Key, often only unlocks one door or room.

Some of the numerous criteria considered while designing a system are:
the brand or manufacturer of the locks and keys (the most important factor of security);
how many locks are in the system;
who is in charge of key distribution; and
the positioning of the doors (exterior, I.T., classroom, etc.).

To activate high-security cylinders, high-security keys are cut on specific, patented key blanks with special key cutting equipment. High-security locks and keys offer the most key control and resistance to drilling, picking, and damage. However, both patented key blanks and key machines are not widely accessible. Patent protection ensures that only authorized persons can have keys reproduced.

A Master Key System allows a single key to operate several sorts of locks (for example, door locks, cabinet locks, padlocks, and so on) as long as the cylinder inside them is the same model. Key duplication is required for these revolutionary, high-security locks.

Cylinders with patent protection increase security while lowering access control costs. Master keyed cylinders provide a framework for key management and are easily linked with electronic locks, which is the best lock for main door.