Mounted on {TAIL ~ the shaft} 30 is {HEAD ~ a viewing or telescopic apparatus V} having a base plate 50 welded or otherwise secured to the shaft 30 
Mounted on is
Mounted on { TAIL ~ the shaft } 30 is { HEAD ~ a viewing or telescopic apparatus V } having a base plate 50 welded or otherwise secured to the shaft 30
REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH REL HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH