Surface cannot be created with nurbs curves by pressing F key

Question

I followed several tutorial to create a nurbs curve, and duplicate it in edit mode. Of course I pressed A key to select all points and F key to create surface. But there was no surface be created, a start point of one curve and an end point of another point were connected instead.

Is there anybody get any idea about this case?

Answer 1

You simply need to use one of the Nurbs Surface types. Add > Surface > Nurbs Curve

A Curve, whether a nurbs or bezier is only a stroke. It can not have volume, it is only ever a line.
A Surface is a full 3D solid that can have volume. All the expected commands will work: Fill F, Extrude E etc.