2040 wall to 45 degrees

I wanted to make a simple but strong shelf for my new computer. The tower is small, for desktop, but I wanted to preserve desk space.

You also need 2040 alu bars in desired length, pluss this part:
https://www.thingiverse.com/thing:2532636

And maybe this:
https://www.thingiverse.com/thing:2545183