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