BELT WAS BRING ROLLED OFF STRUCTURE ONTO A PORTABLE ROLLER. MOUNTED ON A TRUCK. THE BELT WAS BEING PULLED THRU THE DRIVE ROLLERS WHITCH CAUSES THE ROLLER TO TURN. THE BELT HUNG AND STALLED THE PORTABLE ROLLER. THE INJURED CLIMBED ON TOP OF THE BELT DIRECTLY OVER DRIVE ROLLERS. TRYING TO BOUNCE ON BELT TO GET SLACK BELT PULLED LOOSE FROM TRUCK DROPING HIM BETWEEN ROLLERS.