No knob on my Bobcat, so I modelled this one after the headlight with knob, but with a hex in the base to insert the nut to secure it to the switch. This was locked into place using heat and a flat end of a fork. The knob then is screwed into place on the switch, and voila!measured an existing lighting knob from the bobcat, and modelled this up in OpenSCAD. printed at 0.1 layer height, then plan to vapour smooth for injection moulded finish.