Works with a 1/2" wooden dowel with a tight fit and drywall screws to attach them to the wall.
I would recommend printing enough brackets to allow for spans no longer than 14" for strength, your mileage may vary.
Works really great and saves a lot of shelf space. Really easy to print and usually prints in a few hours (i printed 3 at 0.15mm layer height in 3 hrs. Thicker layers will likely be stronger and faster to print).
The author hasn't provided the model origin yet.