Abstract: A lock for use with a nonrotating, flexible sheet key having holes positioned according to a pattern. The lock has a plurality of plates independently slidable for movement along a path generally transverse to the key. Each plate has a pin at a selected location along an edge toward the key for engagement therewith. The pins are aligned according to the key hole pattern to have some of the pins enter into the holes and others contact the body upon movement of the plates toward the key for placing each plate in a consent position. Each plate has an aperture for coincidence with the apertures of the other plates when moved into their respective consent positions for forming a lateral opening. An arm extends through the apertures and is laterally movable within the lateral opening to indicate an unlocked condition.