EMPLOYEE WAS WORKING ON THE COOLOER FOR INSTALLATION OF A NEW CHAIN. WHEN REMOVING SOME OF THE OLD CHAIN PIECES THE BACK PLATE HAD TO BE REMOVED. UPON REMOVAL OF THE LAST BOLT, THE PLATE FELL. BOUNCED OFF OF A SUPPORT ANGLE AND STRUCK EMPLOYEE'S LOWER RIGHT LEG. EMPLOYEE RECEIVED 4 SUTURES TO HIS LEG.