Hooks for 12 mm kitchen rails like IKEA KUNGSFORS

The hooks can be clipped onto the rails so that they cannot accidentally fall off. There are 3 different length. I guess "Medium" is the most common length.

I would recommend printing the hooks with PETG as it is relatively flexible. PLA is too brittle and could therefore easily break when clipped onto the rails. Even if you use PETG, you should be careful when clipping the hooks onto the rails.

Of course, the hooks are only designed to hold relatively light objects.