With this hook you hang up your bike helmet with the top towards the wall, you put it on the wall in one motion by just doffing your helmet. The hook is designed with the Bell Ukon helmet in mind, but should work with others that have a similarly shaped hole at the crown. See the red marks in the image. The screw holes are 60 mm apart and are sized for 4 mm screws. This should print easily in PLA. No rafts or falsework (“supports”) needed. A brim may be useful to avoid warping. There is a bit of design history in the [Helmhaken](https://github.com/ospalh/3d-printing/tree/develop/Helmhaken) folder of my github 3d printing repo. I have added the FreeCAD file, so the sizes (hook and screw holes) can be adapted. This is one of my earlier tries, and i have since learned a few more CAD tricks. Changing the size, especially of the hook part, isn’t as simple as it could be. Sorry.