The first and second channels each have a flange extending from {HEAD ~ one wall} to {TAIL ~ adjacent opposed wall} to define the elongated opening into the channel 
The first and second channels each have a flange extending from { HEAD ~ one wall } to { TAIL ~ adjacent opposed wall } to define the elongated opening into the channel
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH