Once opened, {TAIL ~ the second clamp} 14 is placed around {HEAD ~ the drill stem} and the hinged jaws are closed 
Once opened , { TAIL ~ the second clamp } 14 is placed around { HEAD ~ the drill stem } and the hinged jaws are closed
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH