{HEAD ~ The elongated track} is mounted on {TAIL ~ the tractor} and extends in generally parallel upwardly spaced relation to the water main 
is mounted on
{ HEAD ~ The elongated track } is mounted on { TAIL ~ the tractor } and extends in generally parallel upwardly spaced relation to the water main
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH