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