Organisation hook sized for the Ivar series of shelves from Ikea. Clips on to the horizontal shelf, and is useful for hanging small tools, test leads, etc.
Probably not a good idea to hang anything heavy on them, but at around 8 minutes to print on my Cocoon Create, they're disposable.
Fits on http://www.ikea.com/au/en/catalog/products/S19903042/