An extruded aluminum channel is formed with a wide central T shaped groove and {HEAD ~ narrower outer T shaped grooves} transversely spaced on {TAIL ~ opposite sides} of the central groove 
An extruded aluminum channel is formed with a wide central T shaped groove and { HEAD ~ narrower outer T shaped grooves } transversely spaced on { TAIL ~ opposite sides } of the central groove
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH