Two way screw (bolt)

This is two way thread screw. Its main feature is it has two different threads.
Clockwize thread has 3 spirals and counterclockwise thread has 4 spirals.

Step of both ones is 20mm. So clockwize (hexogon) nut moves at 60 mm per turn and counterclockwise (octagon) nut moves at 80 mm per turn.

It's just good thing to amaze your friends.