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