Edit NURBS > Extend Surfaces

Extends an edge of a surface.

Edit NURBS > Extend Surfaces >

Extension Type: Tangent adds new isoparms to the extended surface.

Extrapolate rebuilds the surface according to the direction and distance specified, but without adding new isoparms.
Distance: Sets the length of extension.
Extend Side: Specifies the sides that will be extended; the start is the U0 and V0 location on the surface. This option is available in the Channel Box after you extend the surface. Select the extendSurfacen node to display the option.
Extend Direction: Specifies the U, V, or U and V directions for the extension to be built. This option is available in the Channel Box after you extend the surface. Select the extendSurfacen node to display the option.
Join to Original: You can turn off this option only when the Extend Side and Extend Direction options are not set to Both. Maya disables the selection of Both for Extend Side and Direction, and causes Extend Surfaces to create an unattached and separate surface.
Keep Original: This option causes Extend Surfaces to keep the original surface when it builds the new one. Turn this off if you prefer to discard the original surface.