In some occasions, the interlocking sequence requires of more than one key to perform it. Key selectors allow to get more than one key from just one, so that the interlocking sequence can be performed without errors.

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