A master-keyed system is perhaps just two or three locks that are not only operated by individual keys, but with an additional key (the master key) that will open them all! This would mean, for instance, that each of three offices could only be accessed by the personnel working within that particular office. The department manager would only need the master key to open any of the three doors, enabling him to carry out his duties in all involved offices more efficiently. A master-keyed system is perhaps just two or three locks that are not only operated by individual keys, but with an additional key (the master key) that will open them all! This would mean, for instance, that each of three offices could only be accessed by the personnel working within that particular office. The department manager would only need the master key to open any of the three doors, enabling him to carry out his duties in all involved offices more efficiently.Once this concept has been grasped, it is easier to understand how much simpler life can be if there are dozens, if not hundreds, of doors involved. It may be more secure to split up a building into zones. Perhaps there might be ‘sensitive’ areas such as laboratories or wages rooms where you want to restrict access — even to master key holders. This might be solved with the introduction of a sub-suite incorporating a sub-master key. This would introduce a third tier to the previously described two-tier system. There is no limit to the number of sub-suites that can be incorporated into a system. However the managing director, or equivalent, could still have a key that opens everything — the Grand Master Key!