The channels are held together by {TAIL ~ one or more cross stringers} which pass through sidewalls of each channel in apertures adjacent to a channel base and are secured to the channel base by securing {HEAD ~ means} of various types 
The channels are held together by { TAIL ~ one or more cross stringers } which pass through sidewalls of each channel in apertures adjacent to a channel base and are secured to the channel base by securing { HEAD ~ means } of various types
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH