PIPING GREW WAS SETTING UP TO FUSE DRISCO PIPE. FUSIN MACHINE EQUIPMENT WAS BEING UNLOADED FROM ABOOM TRUCK. OTHER HANDED EE THE HENTER PLATE WHICH WAS INSIDE ITS CARRIER RACK ASSEMBLY. WHEN H E SET THE UNIT ON THE GROUND THE HEATER PLATE ROTATED AND CAUGHT HIS R. MIDDLE FINGER BETWEEN THE ALIENMENT EARS ON THE PLATE AND THE CARRIER RACK FRAME.