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