The underside of {HEAD ~ each channel base} provides a relatively large lateral dimension for fastening {TAIL ~ individual channels} together by means of a transverse stringer or strut 
The underside of { HEAD ~ each channel base } provides a relatively large lateral dimension for fastening { TAIL ~ individual channels } together by means of a transverse stringer or strut
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH