If you're clumsy like me, you'll notice how hard it is to keep the bowden tube straight while you're trying to thread an M4 nut into it.

This is a tool that keeps your bowden tube aligned with the nut for threading. It also features a hole at the bottom for re-drilling the bowden tube after the nut has squeezed the hole smaller.

1. Print.
2. Stick nut into hexagonal recess.
3. Snap the pieces together.
4. Gripping the PTFE tube with your hand, push it in from the top and twist it into the nut until you notice the Bowden tube pushing the pieces of the jig apart.
5. With the jig still assembled, use a drill bit to re-drill the hole of the PTFE tube which should have shrunk a bit from the compression caused by threading.