{HEAD ~ A rubber thread} includes in cross section a first rubber portion and {TAIL ~ a second rubber portion} 
{ HEAD ~ A rubber thread } includes in cross section a first rubber portion and { TAIL ~ a second rubber portion }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL