Nut blocker for 3Drag/K8200 easy tool switching

On 3Drag/K8200, switching the extruder with other tools (such as Dremel, comparators, lasers, etc.) is really uncomfortable: the two square nuts that slide in the profile are not very visible, and every time you have to redo the perfect "centering" of the tool along the aluminum profile.

I then made €‹this simple "nut blocker", to keep the two square nuts in the correct position, allowing an easier replacement of the tools.