Our heater has a knob to turn it on or off. The knob broke. I went to a hardware store and an appliance store, and neither had ever heard of the brand (“Hammel”), even. So I printed a new one.

It works. It was only slightly difficult - I used Rhino to make the STL file (a little extruding shapes, boolean difference and union, I think that was about all I needed; difficulty level 4/10), then Makerbot’s software to convert the STL to an X3G which our particular printer needed (Makerbot Replicator X2), and that was about it. Thanks to Ayman and Cati for help!

It’s on Thingiverse too so if you have the same janky old heater you can print it yourself.