A neat little add-on for your trusty Grundtal wall shelf.

The cut-outs for the round bars of Grundtal don't fit perfectly but well enough to stop stuff from sliding around, as the Grundtal is not always perfectly aligned it was the closest I could get, but it should do. I printed this with PETG but ran into extrusion and cooling issues, should print perfectly fine with calibrated filament and slowed down, or just use PLA, as long as you don't put heavy loads on it.

The top part slots into the corner holes of the hex grid of the bottom part so it doesn't slide around, and that's pretty much it