It's nowhere near as comprehensive as a hardware store nut and bolt thread checker, but if you've got a 3D printer and just a handful of fastener sizes you commonly work with, this is for you. Prusa Printers has uploaded files for this metric screw measuring device, with a range from M2 to M5, from 4 to 50mm:

It's admittedly not an ideal design, but whaddaya want, your money back?

The Good:

"Quickly sort and measure metric screws and bolts in sizes ranging from M2, M2.5, M3, M4, or M5 with lengths from 4mm to 50mm. Screw diameter sizing is a simple go/no-go clearance check which is faster than threading in a screw."

The Bad:

"Note that this doesn't tell you anything about screw pitch, but all of my metric stuff is standard coarse thread so I'm okay with this. If you want to confirm the exact thread, check out sneaks' original design with threaded inserts or check out registeredthing's remix with nuts as inserts."

via Gareth's Tips