{HEAD ~ The unitary metallic plate} is formed into a panel, {TAIL ~ channel walls}, at least two feet, and at least one external reversing bend 
is formed into
{ HEAD ~ The unitary metallic plate } is formed into a panel , { TAIL ~ channel walls } , at least two feet , and at least one external reversing bend
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH