{HEAD ~ The force} is used to determine {TAIL ~ the density} of the insulation, which, in turn, is used to determine the thermal resistance or R value of the insulation 
is used to determine
{ HEAD ~ The force } is used to determine { TAIL ~ the density } of the insulation , which , in turn , is used to determine the thermal resistance or R value of the insulation
HEAD HEAD HEAD HEAD HEAD HEAD REL 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