The clamp plate extension has {HEAD ~ a concave, circular toothed depression} forming one half of a socket to hold {TAIL ~ a ball} 
The clamp plate extension has { HEAD ~ a concave , circular toothed depression } forming one half of a socket to hold { TAIL ~ a ball }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL