I am using an Ikea Lack table beneth my A1 and found it pretty wobbly.
To counter it I looked for corner brackets for Ikea Lack tables and weren't quite happy with the results.
So i designed my own one! Fitted four of those in the corners and this thing is not wobbly anymore. Mission success!

Features:
- Lots of holes for screws, I used the outer ones
- three-directional stabilizing
- easy to print
- no unnecessary parts