One flange 46 has a depending lip 48 and {HEAD ~ the other flange} 47 has {TAIL ~ an upstanding rib} 49 to seat within the channel flanges 40 securing the tray from downward movement 
has
One flange 46 has a depending lip 48 and { HEAD ~ the other flange } 47 has { TAIL ~ an upstanding rib } 49 to seat within the channel flanges 40 securing the tray from downward movement
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH