Hello,

Many thanks for your explanations Michael, this lets me understand and learn a bit more :-)
Both methods (yours and Pilou's one) was very good to make my ellipse perpendicular to my surface.

However I prefer to draw directly on the surface with "object snap" enabled because this surface is not really planar, so drawing directly onto it lets the ellipse axis (say hole axis) exactly perpendicular just as I needed.



Thank you very much again for your so precious help ! :-D

Best thinking and cordially yours,
Guy