THE REAR CENTER SHOULDER BELT HOOKS OVER A PIN ON THE BUCKLE. THERE IS NO POSITIVE LOCK OR UNLOCK MECHANISM. WE FOLLOWED THE INSTRUCTIONS IN THE OWNER'S MANUAL ABOUT HOW TO CONNECT THE REAR CENTER SHOULDER BELT. THE SHOULDER BELT SUDDENLY DISCONNECTS WHEN THE PASSENGER HAPPENS TO MOVE A CERTAIN WAY. THE BELT RAPIDLY RETRACTS AND THE METAL BUCKLE HITS THE RIGHT REAR PASSENGER IN THE FACE OR EYE. A POSITVE LOCK SHOULD BE INSTALLED SO THE REAR CENTER SHOULDER BELT WILL STAY LATCHED UNTIL IT IS INTENTIONALLY RELEASED. THIS CAR WAS RENTED FROM HERTZ COMPANY IN MAUI, HAWAII, SO I DO NOT KNOW DETAILS SUCH AS VIN NUMBER. *AK