The extension surface can be merged as part of the original surface, or appended
as a second surface adjacent to the original surface.

The following prompts are displayed.

Specify Extension Distance

Specifies the extension length.

Expression

Enter a formula or equation to specify the length of the surface extension. See Constrain
a Design with Formulas and Equations.

Modes

• Extend. Extrudes the surface in a way that tries to mimic and continue the shape of the surface.
• Stretch. Extrudes the surface without trying to mimic and continue the shape of the surface.

Creation Type

• Merge. Extends the surface the specified distance without creating a new surface. If the
  originating surface is a NURBS surface, the new extension surface will also be a NURBS
  surface.
• Append. Creates a new extension surface that is adjacent to the original surface.