I don't really have a close up of the corners pre-paint. Now the corners are sharp 90 dregrees. I welded the skins on to the 1-1/2" x 1-1/2" square tubes directly. Nothing in between (glue wise). The point on the outside of the box were the two skins met top/side came out pretty clean after grinding, but to insure there wouldn't be any cracks, I used JB Weld for that. After priming and painting I use silicone sealant and basically covered the entire inside of the box making it water proof you could say.