Note: This is thing is not maintained on here any more, further development/support it will happen on its Youmagine page. My mother (who's a teacher) keeps her personal stash of blackboard chalk in a small container. In the past she had the problem that the chalk could freely rotate and fall around in that container, which led to some broken pieces and a lot of chalk dust. When I introduced her to my newly acquired 3d printer, she immediately thought of this specific problem and we designed a solution for it, a thing to use as a organizing part between the layers in her box to keep the pieces in place.The STL file is an organizer thingy sized 58mm wide and 40mm long, with 5 grooves of 10mm diameter. If you want/need different measurements, you can adjust the w and l parameters in the provided OpenSCAD file.