{TAIL ~ The frame} may comprise {HEAD ~ a base frame} and a operating leaf frame overlying the base frame 
{ TAIL ~ The frame } may comprise { HEAD ~ a base frame } and a operating leaf frame overlying the base frame
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH