Master Key
A SINGLE KEY FOR MANY DOORS…
A master key system allows for different access combinations using locks or keys and based on user access levels. There are several types of keying:
Diferent Keying

Each lock in a group is opened by a separate key.
Users must have separate keys to open each lock.
Similar Keying

A single key opens all of the locks.
Master Keying

2-level key system

3-level key system
For practical reasons, locks with similar and different keying can be created that are opened by a single master key: