How to set the drive to keep one part's Z axis parallel with a point's Z axis at left humerus？

[Taejun (MA Taejun)]

Hi, I want to build an exoskeleton. Here are some parts of my exoskeleton.

A is a point located at the humerus of the human model. I already made Part II rotates around the x-axis of point B at Part I. C is at Part II. Now I want to make a driver to keep the Z axis of point C always parallel with the Z axis of point A. But I don't know how to do it, could you give me some examples? Thanks！
Best，
TJ

[Bjorn (Bjørn Keller Engelund)]

Hi @Taejun

You can find examples of how to join objects in the tutorials link I send you in another post.
For more tips on how to join exoskeletons with the human model please have look hereon our wiki page to read more.

Best regards,
Bjørn