In {HEAD ~ the case} of {TAIL ~ a U shaped staple}, the plug of filler material would be joined to the cross member joining the staple legs 
In { HEAD ~ the case } of { TAIL ~ a U shaped staple } , the plug of filler material would be joined to the cross member joining the staple legs
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH