Master Key Systems
Master key systems create two or more keys that are capable of varying levels of access within a given system. Under a master key system, one key may be capable of opening all doors within that system, while another key is only capable of opening a single, specific door within the same system.
For example, hotels often employ master key systems, in which hotel staff carry keys that can open the doors to every room, while guests receive a key that can only open the door to the room in which they are staying. In this way, each lock has several keys that will open it, and each key has different capabilities in terms of which doors it can open.