Construct a redefine surface

Choose Surfacing tab→Surfaces group→Redefine Surface .

Select the faces to be replaced, and then click the Accept (check mark) button.

Adjust the continuity settings or command options settings and then click Preview.

(Optional) Insert a sketch by doing the following:

1. Select the Insert Sketch Step, and then specify the plane type for which the sketch will be created on.

2. Select a location for the sketch or pick U/V curve for which you desire to be included in the new sketch, and then click the Accept (check mark) button.

In the example below 1 is the replaced surface and 2 is the inserted sketch generated from the selected U/V curves on the surface by the Redefine Surface command.

Finish the feature.