These holders allow you to hang smaller cable spools of up to 10 cm diameter under an IKEA Lack bookshelf.
I have one of those shelves over my work desk and I needed a place for my cable spools so that they are always accessible for my DIY projects. These holders clip to the sides of the shelf. A steel or aluminum tube can then be clipped into the holders. For adding or removing spools, just unclip the tube again.
Print with ABS if possible as PLA seems to be to stiff for the clip in/clip out.
Creative Commons Attribution Noncommercial Share Alike