This is a 3-point bracket. Use it to build a frame, add a tabletop, or make a box. The outer dimensions are pictured. All walls are a 1/4" thick. The screw/bolt holes are 1/8". The screw head hole is inset to 1/8" and is .35" wide.
You can scale to whatever dimensions you like.
Disclaimer: Use this part in your build at your own risk. Load test have not been performed.