Locking device with dual headed bolt for reciprocal locking of individualy tiltable backrests

A locking piece (10) attaches to a motor vehicle seat back and has a first locking element (54) that moves reversibly from an unlocking position into a locking position and engages a first counter locking element (72) on the other motor vehicle seat back. The locking piece has a second locking element (56) that engages a second counter locking element (70) during locking.