You ever need to lay out a hole before drilling into something?  

In my case, I was drilling into a large plastic bluetooth speaker to install a couple switches & I wanted to make sure the holes were well centered on the space & also, I wanted to see how they would look before committing to drilling holes, so I printed these the size of the hole and also the size of the switch (standard '12v, press in from the front' style automotive switches) so I could be sure I wanted it there.

This is really simple, but something I actually needed this past weekend, so I knocked it out; I only printed a couple sizes (the ones I needed), but I'm including all of the sizes in my set.  You could use them with spade bits as well & I printed them with the 0.2mm nozzle, but I'm quite sure that was overkill (it was still installed & I figured it was easier than swapping it out - this is why I only printed the couple I needed, though, as this took a lot longer than the standard 0.4mm would have).

The hole in the center is so you can mark [whatever you're drilling] with a pencil to know where to put the tip of your bit & my Forstners are imperial, so that's what I did, but these were super-easy to make, so I skipped making a metric set.  If for some reason you can't make the metric set yourself but want that version, just let me know & I'll knock it out for you (let me know the diameters of all the bits in your set or at least the ones you need so I don't miss the one you needed 😉).

Happy making!