Modular wrench holder with interchangeable labels.
One set of labels includes a blank one, to write / emboss custom label on it.
The labels in photos were touched up with a Sharpie white pain permanent marker.
The holder also seems to work good enough to store some spare oversize drill bits (see picture).
The author remixed this model.
The modules are wider so that there is now enough space to attach a label. The magnet holes are for 8x5 mm magnets (because that's what I had lying around)