Extra support bracket for a shelf, 3 connecting pieces made to go with a wood profile (width: 30.30mm / height: 19.20mm), 45% degrees angle. Secure shelf to bracket with a M4 screw and nut. Modeled with Blender. Printed with PETG + carbon for extra rigidity and strength.

I also recommend treating any filament with added carbon to be surface treated for safety.