I was teaching a robotics workshop, and the arduino clone that came with the kit has some extra headers for attaching jumper wires (good), but the headers aren’t numbered according to what microcontroller pin they connect to (bad). So I took about an hour (including a bunch of prints that weren’t quite the right size) and made up these little dongles that fit over some unused other headers. My students were thrilled…

And here it is in place.

I probably should have used Hershey text, because most of the time for making it was the engraves…