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