A small hook that clips onto a standard bathroom heating ladder (20 mm diameter and 20 mm min distance between rungs). It is handy for hanging towels or anything else that needs to dry. When you clip it the right way (see the pictures) there is basically no chance it will come off because of the weight of the hanging object. Experimentally verified with PLA on a heated (!) ladder :).
The author hasn't provided the model origin yet.