said fourth plane of {HEAD ~ said edges} of said open top side of said clasp lower part being parallel to {TAIL ~ said first plane} of said upper surface of said clasp upper part  
said fourth plane of { HEAD ~ said edges } of said open top side of said clasp lower part being parallel to { TAIL ~ said first plane } of said upper surface of said clasp upper part
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH