Each C shaped channel 18 includes a pair of opposed generally L shaped legs 34 and {HEAD ~ an interconnecting portion} 36 extending between {TAIL ~ legs} 34 
Each C shaped channel 18 includes a pair of opposed generally L shaped legs 34 and { HEAD ~ an interconnecting portion } 36 extending between { TAIL ~ legs } 34
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH