You can create a surface or polygon mesh by extruding a profile curve along a guide or rail curve. This and similar operations are sometimes called rail or sweep. If the input curves are closed, the resulting object will be closed in the corresponding direction; if they are open, you have the option to close the result.
To extrude a curve along a curve
Select the profile curve first, then add the guide curve to the selection. You can select curve objects as well as U or V isolines, U or V knot curves, boundaries, surface curves, and trim curves.
Choose one of the following commands from the Model toolbar:
If you didn't select a profile and guide curve in step 1, you can pick them now. An object is extruded and the Extrude Curve property editor opens.
Adjust the parameters as desired. For more information, see Extrusion Property Editor (Curve along Curve) [Properties Reference].
Extrusion showing the profile curve (A), the guide curve (B), and the result.
Surf. Mesh