I built a light equipment case out of plywood and needed a carry handle. This one seems sturdy enough... Self-tap with two wood/metal/sheetrock screws to mount. I used 2" sheetrock screws, and they hold well.
I also wanted to protect the corners from knocks. These work great with #6 x 1/2" flat-head screws. Longer than 3/4" screw tips may interfere with one another. The x4 .stl file is four identical copies of the single corner, for easier printing of full sets.
No supports needed.