Menu: Geometry->Edit->Hole surface

With this option you can select one existing NURBS or planar surface and a set of closed lines that are inside it and that form one or more holes. The lines may be created by an intersection with another surface. The holes will be added to the existing surface.

It is possible to define the holes also selecting other surfaces, getting its lines to hole the first surface.

Hole NURBS surface

NURBS surface hole