The external corner formative member 1, wherein the angled corner plate portion is formed flush with {HEAD ~ the front plate} of each of {TAIL ~ said groove portions} 
The external corner formative member 1 , wherein the angled corner plate portion is formed flush with { HEAD ~ the front plate } of each of { TAIL ~ said groove portions }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL