Select the geometry with rectangle selection or clicking on surfaces and type ‘delete’ in command line or click on ‘Edit->Delete’ menu.
Figure: Remove parts
In the following case, the holes must also be removed. For this, we must remove the trimmed curves of the NURBS surface.
Figure: Remove surfaces
Select the surface with holes and click on menu "Geometry -> Surface -> UnTrim".
Figure: Untrim surface
Select one curve of the hole and press 'Enter'.
Figure: Surface without hole.