The flexible sheets have {HEAD ~ a width} which is greater than {TAIL ~ the width} of the insulating boards so that longitudinally extending edge portions of the sheets project outwardly from the edges of the insulating boards 
is greater than
The flexible sheets have { HEAD ~ a width } which is greater than { TAIL ~ the width } of the insulating boards so that longitudinally extending edge portions of the sheets project outwardly from the edges of the insulating boards
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH