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