This is a loom for creating rubberband bracelets. It is designed to fit two base plates together for longer projects. I created this from scratch so that the interconnecting pieces fit together and used Draco155's thing as a guide but that one does not fit together without a lot of filing and the posts break off too easily. My first attempt was the orange base plate (see photos) but the posts were also too easy to break off, so I enlarged and strengthened the posts so those don't break off as easily. The purple base plate is the final version (see photo).
I printed this out at .2mm layer height, 4 shells (you want it strong) and 10% infill. It shouldn't need any sanding - mine fit perfectly.
I printed two out at a time on my Rep 2, that works well, see the thing file. I also changed the filament for the posts, I think it adds a bit to make those a contrasting colour; wait for the extruder to stop going around the outer edge of the baseplate then switch colours.