In some occasions, the interlocking sequence requires of more than one key to perform it. Key selectors allow to get seven keys from just one, so that the interlocking sequence can be performed without errors. In addition, it may be necessary to activate an electric signal mechanically (key on an electric device).

As an example, in a key selector with eight keys, when one of the cabinet locks is released, the other seven are trapped and cannot be released. If the free key is inserted and turned, the other seven can be released and, consequently, the former is trapped.