The blue sheet metal was put on first, then the white to overlap it. I used 1/8" pop-rivets left over from an airplane project. I pop-riveted into the 90-degree sheet metal at the top and sides, and into the wood braces. The writing on the side shows where the horizontal braces are and where the wires are. Pop-rivets heads were touched up with silicone caulk to prevent leaking. The steel panels weigh 2-2/3 more than aluminum.