You can replace faces in a surface or solid body with new surface bodies using the Replace Face 
tool (Surfaces toolbar).
The replacement surface body does not need to have the same boundaries as the old faces. When you replace a face, adjacent faces in the original body automatically extend and trim to the replacement surface body, and the new face trims. See the examples below for information about how to use the Replace Face tool.
Replace Face allows you to do the following:
- Replace a single face or set of connected faces with a surface body.
-
Replace more than one set of connected faces with the same number of surface bodies in a single operation.
You must list the face sets for Target faces 
in the same order as the corresponding Replacement surfaces . Replace Face identifies the pairs of original and replacement faces and performs the replacement.
-
Replace a face in a solid or surface body.
The replacement surface body can be of the following types:
- Any type of surface feature such as an extrude, loft, fill, and so on.
-
A knit surface body, or a complex imported surface body.
-
Usually wider and longer than the faces you are replacing. However, in some cases when the replacement surface body is smaller than the faces for replacement, the replacement surface body extends to meet the adjacent faces.
The faces for replacement have the following characteristics:
- Must be connected.
-
Do not need to be tangent.