{HEAD ~ a clasp upper part} having {TAIL ~ a dish shaped cross section} to provide an upper surface and an open underside with downwardly facing edges 
having
{ HEAD ~ a clasp upper part } having { TAIL ~ a dish shaped cross section } to provide an upper surface and an open underside with downwardly facing edges
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH