Hi Steve and Michael,

Thanks for your answer and your help both.

Yes, the Danny's video is very good to learn this tangent calc for drafting ! This helped me a lot with my understanding of this thing.
And this inside calc function is quite cool, thanks Michael to do a so good work for us !

But my piece was pretty complicated, so this did not works at all in my present case.
Anyway I found an other easy way : "sweep" function with my drafted shape as the profile and the shape of my piece as the rail.
So before I can have more time to learn better to try mastering this wonderful software, and before Michael can implement his "tapered extrude" function, this did the job for me.

Thank you very much again,
Best Regards,