EE WAS HOLDING CRIB BLOCK AGAINST FEEDER FLIGHT WAITING FOR CAR TO PULL UP AGAINST IT. EE OPERATING FEEDER (JOGGING CHAIN) WAS TOLD TO HOLD IT. FEEDER OPERATOR REVERSED FEEDER CHAIN CAUSING CR IB BLOCK TO GO UNDER BUMPER OF SC & CAUGHT INJUREDS HAND BETWEEN CRIB AND FEEDER FRAME.