How to fix errors in Multi-Sections Surface in CATIA V5?

When I try to create a surface using Multi-Sections Surface I get an error saying:
"Loft operator: the projection of the point of a section or a guide is outside the spine limits." It also says: "Extend the spine" , what does it mean? How can I do it?

2 Answers

It's because one of the guides (end one) extends beyond a section end point.
It's a bad way of creating the surface anyway. There are better ways

The image is not clear but i am assuming that the vertical 3 are guides and there are 2 horizontal sections. I think the error is due to guide 3. There is a sharp point on it. May be because of that software is not able to compute the geometry. Try to give round at that point while drawing guide 3. It may resolve the problem.