EE WAS PUSHING SLATE BLOCKS DOWN ROLLER CONVEYOR WHEN A COWORKER ATTEMPTED TO ASSIST HIM. COWORKER TURNED POWER ROLLERS ON TO ADVANCE BLOCKS INTO MILL OPERASTION. INJURED EE WRONGLY USED FREE SPINNING ROLLERS AS A MEANS TO STABILIZE HIMSELF TO PUSH BLOCKS DOWN CONVEYORS. HIS HAND WAS PINCHED BY A BLOCK ENTERING SAWING AREA.