A very ergonomic and easy to print knob which captures hex nuts. The size can be adjusted to accommodate any size of nut (or bolt).
Adjust the parameters in the customiser to suit your needs - remember to add a little extra clearance (0.5-1mm) on the hole and hex nut cut out so that everything will fit together after the print contracts a little.
I've included the appropriately sized .stl files for an M3 and M4 nut (or bolt).
The inspiration for this came from the adjustment dial on my Terstial (Ikea) desk lamp.