{HEAD ~ a thin flat plate} having an inner edge, an outer edge and {TAIL ~ two flat surfaces} 
{ HEAD ~ a thin flat plate } having an inner edge , an outer edge and { TAIL ~ two flat surfaces }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL