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