EMPLOYEE WAS WORKING W/ CO-WORKER INSTALLING WEATHER PROTECTION AROUND THE TOP OF THE TUB BE-TWEEN THE REVOLVING FRAME. THEY WERE MOVING A 5'X 12' PLYWOOD PANEL FRAME IN A WALKWAY BETWEEN THE TUB AND A STACK OF CRIBBING. THE PANEL HIT THE CRIBBING STACK WHILE IN MOTION AND THE JAR HYPER EXTENDED EMPLOYEE'S WRIST CAUSING A SPRAIN. EMPLOYEE IS ON LIGHT DUTY 10 DAYS.