Nice example Pilou!

Another method to do that is instead of using one star and 2 rails, you can use one rail and 2 stars, like this:



Select those 2 stars (and make sure they are placed away from the bounding box around the rail path), and the run Construct / Sweep, and pick the rail curve to get this:



With this method you don't have to create a pipe first...

But sometimes it can be nice to extract edges for further constructions in different cases, that is a good idea to keep in mind.

- Michael