> About the Curve start /curve End on a rail or path is this image more clear ?
> Of course curve Start, Curve End , and rail -path) can be any curve !

Hi Pilou, you can use sweep for this, choose the start and end curve, run Construct / Sweep, then select the rail.

But it is more typical to have the rail running down the center of the profiles, it is somewhat easier to control things that way. Sweep with one rail will slide the shapes along the path, and it will reorient them to follow the path. When you have the rail only on one side of the shapes, the other end of the shape tends to move quite a bit when it is reoriented (kind of like it swings around a lot since it is far away from the path). With a path down the center the shapes swing in a more "balanced" way around their center points. Let me know if this needs more explanation.

But you probably won't get a very good result from the curves in your image, there is just a little bit too many things going on there, there is the curve of the path and then having a circle change into a rectangle which is a major shift. To control the resulting surface better in this case you would normally need to use some more curves to define what you want better and maybe build it in a few sections.

- Michael