NEW 3 face corner bracket: https://www.printables.com/model/1390968-strong-corner-bracket 

Simple 55 × 55 × 15 mm corner bracket designed for M3 screws. Easily scalable for larger applications.

Features:

• Pre-sized for M3 screws
• Compact and clean design
• Easy to scale in your slicer for M4, M5 or bigger hardware
• Can be printed in PLA, PETG, or even ABS for added strength

Perfect for both quick fixes and larger modular setups where you need a reliable corner connection.