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