I want to join them like this but the rotated part should be exactly the same height as the two parts (while also connecting exactly to the sides, pretty much as accurate as possible).
The second image was made using GapFill. I wasn’t able to produce the results I wanted. It’s not filling in an area I’m trying to do; the final result will connect to the top edges of both parts while maintaining a consistent height between all three parts
If you need the Part to match up to all four corners, I think the current angle is impossible to have the same thickness due to it forming a right triangle and Pythagorean’s theorem. I could be wrong though…
I wasn’t sure though so I asked buildthomas (thanks), who said if you changed the angle a bit and allow some overlap at the lesser angles, it would work.
Edit: Here’s another shot at the solution, note the overlap circled