More complicated setups are also possible. For example, if there are cleaners in the office building, and each cleaner only cleans one floor, the cleaner for a each 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, cleaner 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.