{HEAD ~ A second base plate} 51 is rotatably mounted on the first base plate 50 having a centrally disposed pin 52 extending into {TAIL ~ an opening} 53 in the base plate 50 
{ HEAD ~ A second base plate } 51 is rotatably mounted on the first base plate 50 having a centrally disposed pin 52 extending into { TAIL ~ an opening } 53 in the base plate 50
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH