This is a holder for sandpaper designed to hold special "metal" sandpaper used to remove "grates" / "burrs" on steel edges of skis, prior to filing. In danish this is called "smergellærred", in english, I believe it is called "emery cloth". There are a number of ways to remove the burrs, which are often too hard to remove for the files. In my experience, emery cloth is the easiest to handle. What I have been doing until I printed this model was to put the emery cloth between my file and the edge, in order to maintain the 90 degree angle. However, it meant a lot of changing of the cloth. This holder is designed to allow you to use the entire width of the emery cloth strip, while maintaining a 90 degree angle to the metal edge. As you can see from the photos, I have tested this (on about 10 pairs of skis), and it works very well, and allows you to use the file for the finer work of filing/tuning the edge. Attribution: This uses the Thread library. Its included in the source. Printed in 0.3mm layer height 15% PLA worked well. You should split the STL file in your slicer and place each part on the bed. You need support to print the biggest part.