I really liked the style of the hook in the source ( by McUsher), and I needed something to hang my backpack on many different desks, as I travel all over for work and needed a hook that would match pretty much any desk ( on mine sites there tends to be too much dirt tracked around to want to put your backpack on the floor). So, I remixed his cool idea.
This hook at this size will just fit over a 2x4, which is thicker than most of the desks I have generally encountered. I recommend using 6 shell layers for strength. I used 50% infill (cubic) but I feel like this could be played with more than the shell layers. It easily holds my 20kg backpack without any strain.
If anyone is interested in getting a copy of the .step file or .sldprt, let me know.