A skeleton key (or master key) is a key that can open all of the locks in the set. For example, in an office building, each employee would have a key that only opens his/her office, and the manager or owner would have a key that opens all of the offices in that building. More complicated setups are also possible. For example, if there are janitors in the office building, and each janitor only cleans a particular floor, the janitor for a particular floor could have a sub-master key that opens only the offices on that floor, while each employee still has a key that opens only his/her office and the manager still has a key that opens all of the doors. The exterior doors might also be configured so that they can be opened by any employee key, janitor key, or the manager's master key. The more complicated the setup, the more important it is to use locks that have a large number of key possibilities. Disc-detainer locks are especially suitable for master keying due to their large number of key possibilities.