each of {HEAD ~ said sockets} has a cam member contained in the other of said pair of {TAIL ~ holes}, and 
each of { HEAD ~ said sockets } has a cam member contained in the other of said pair of { TAIL ~ holes } , and
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH