I was missing the hooks for the Pegboard (http://www.pegboard.perfonet.de/de/das-pegboard/) I am using.
size: 120 x 60 x 0,5 cm
perforation: Ø7 mm
hole spacing: 25,4 mm
Source: https://www.tinkercad.com/things/gd2YuYFwI4F
Instead of the original one, which can be printed flat, this one needs to be printed standing with support for the straight hooks at least.
The caliper holder is fine to be printed without support (based on the quality of your printer) and the same for the curved top pegboard hooks. If you want to have a very clean bottom surface, add support for them too.
And do not forget adding a magnet, which makes this whole build awesome :D and safe.
The author remixed this model.