The individual structural member of the invention includes {HEAD ~ a pair} of {TAIL ~ parallel panels} which are spaced from each other to define a cavity therebetween 
of
The individual structural member of the invention includes { HEAD ~ a pair } of { TAIL ~ parallel panels } which are spaced from each other to define a cavity therebetween
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH