Master systems are a way to pin cylinders, that allows for multiple levels of users. It gives the holders of top level blanks access to everything, but restricts lower level holders only to what they need access to. For instance, the owner of multiple business locations can hold one blank to all of the doors at all of the locations. Each branch manager can hold one blank that gets them into all doors at their location only. Department heads can hold a blank that gets them into all doors that pertain to their department at their location. And opening / closing associates can hold a blank that gets them into the exterior doors only. Further more, maison keying is another way of pinning cylinders that will allow a holder to have access in a different way. In the same example, a cleaning person can be issued a blank that will get them into the exterior doors at all locations, and into a cleaning closet within each building. The blank will operate nothing else, even what the lowest level associates have access to. A mathematical system has to be created to maintain the integrity of the system and to insure that the blanks only operate what they are intended to operate. The downside to the convenience, of a master system, is that they are inherently less secure with standard hardware. The adding of pins into the cylinders also adds more shear lines for the cylinder to be opened with. Master pinning, when coupled with high security hardware is the ultimate in convenience and security.