I needed an S hook for the Ikea Grundtal rack (http://www.ikea.com/nl/nl/catalog/products/70011397/), one that snugly fits to the rack.

Here's a parametric model. There's a parameter for adjusting the snugness; this further closes or opens the top curve of the hook.

Update: added parameter to print multiple copies. Just enter the width and depth of the print bed.