The ribbon has {HEAD ~ a small thickness} to prevent {TAIL ~ obstruction} of the elements bordering the top flange and the upper surface of the top flange 
to prevent
The ribbon has { HEAD ~ a small thickness } to prevent { TAIL ~ obstruction } of the elements bordering the top flange and the upper surface of the top flange
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH