Hi ed, sorry I'm not sure that I'm really fully understanding what you're describing again.

> I can't just draw an upper rail from the beginning because I
> want a soft curve that starts on the floor, gets up and then
> gets down again.

If you know the kind of shape you want, then why is it that you can't draw a curve that has that shape?

You may need to do some various kinds of editing on the curve, like placing in a bunch of points for the path and the moving control points up and down in elevation to give it the up and down form that you want.

Then when you have the curve that has the softness and up and down shape that you want, you can then build a surface from it using the technique I showed there, where that curve will become one edge of the generated surface.

You can create curves that are not planar in MoI - it's easiest to initially start out with a planar curve but you can edit individual points in elevation to create a curve that goes up and down like it sounds like you want.

- Michael