First and second arms are pivotally attached to the base and arranged to move to {HEAD ~ a closed position} adjacent {TAIL ~ the positioning means} and an open position away from the positioning means 
First and second arms are pivotally attached to the base and arranged to move to { HEAD ~ a closed position } adjacent { TAIL ~ the positioning means } and an open position away from the positioning means
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH