A feature of the invention relates to {HEAD ~ the material} used on {TAIL ~ the contacting surfaces} of the base member and the flaps 
used on
A feature of the invention relates to { HEAD ~ the material } used on { TAIL ~ the contacting surfaces } of the base member and the flaps
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH