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