In addition {HEAD ~ the last pin} can rock about {TAIL ~ a lengthwise axis} and is locked in rocked position by a wedging system  
rock about
In addition { HEAD ~ the last pin } can rock about { TAIL ~ a lengthwise axis } and is locked in rocked position by a wedging system
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH