How to trace back the rail for a sweeping an object

Get back the rail of sweep.3dm (213.8 KB)
Can I get back the path line of this hand rail?

In your case it is simple. The object is nicely aligned on the origin and the rail appears to be a helix.

  1. Draw a vertical line from the origin upwards.

  2. Draw lines from the centers of each end of the swept surface to the vertical line.

  3. Create a helix with one turn

helix.3dm (245.2 KB)

PS: Instead of sweep, you might also use the Pipe command to create a round pipe around a curve.