A pair of elongated connector pipes each having one end portion connected to {HEAD ~ the support structure} for {TAIL ~ movement} along the track 
for
A pair of elongated connector pipes each having one end portion connected to { HEAD ~ the support structure } for { TAIL ~ movement } along the track
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH