The pair of flanges and {HEAD ~ the pair} of {TAIL ~ webs} form a closed sectional part 
of
The pair of flanges and { HEAD ~ the pair } of { TAIL ~ webs } form a closed sectional part
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH