I was asked to make a backdrop for a wedding (see attached below) but the issue is I had to make it break down small enough to fit into a car, so I designed some hidden brackets to assemble the 45 degree miters without requiring any tools (just wing nuts and bolts).

This final design screws into the back of the miter using short wood screws and then uses M5 bolts and wing nuts for hand assembly.

When attaching the brackets to the wood, ensure the miter is at the right angle, make sure the seam of the two halves lines up with the seam of the miter, then screw down in the final assembled position. Once the wood screws are in, you should be able to take apart and reassemble the bracket. After that, use M5 bolts and wingnuts to tighten the brace.

This is the end product goal (for reference only), hidden hardware but breaks down to smaller pieces.