 A practical attack exists to create a working master key for an entire system given only access to a single master-keyed lock, its associated change key, a supply of appropriate key blanks, and the ability to cut new keys.Locksmiths may also determine cuts for a replacement master key, when given several different key examples from a given system.A Maison key system is a keying system that permits a lock to be opened with a number of unique, individual keys.