Sweep one or more profile curves along two path curves (birail)
Select
Surfaces > Birail > Birail n Tool
based on how many profile curves you want to use (1, 2, or 3-or-more).
Click the curve(s) you want to use a profile curves, then click the two rail curves.
Instructions appear on the help line at each step.
Related topics
Skin a surface across profile curves
Sweep a profile curve along a path curve
Parent topic:
Creating NURBS surfaces