{TAIL ~ The edges} of the channel may be provided with {HEAD ~ flanges} 28, 30, similar to the flanges 16, 18 
{ TAIL ~ The edges } of the channel may be provided with { HEAD ~ flanges } 28 , 30 , similar to the flanges 16 , 18
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH