Offset Shell Face
Insert
Shell/Offset
Use this command to offset one or more faces
of a shell. The shell can be an open or closed shape. The required inputs
include the faces to offset and the offset distance.
Optional inputs include reattaching side faces after the offset and attaching and deleting offset attributes to individual faces.
Faces - Select the face(s)s to offset.
Offset - Specify the offset value. A negative value indicates an internal offset. A positive value indicates an external offset.
Side Faces
Use this option to determine how side faces (if any) are created. Side faces are used to reconnect the offset face to the source shape.
Do not create - Edges are exploded and the face is offset. The result will be a disconnected face or shape.
Create - All bounding edges are recomputed. Side faces are created where required.
Force - Side faces are created in all cases. Bounding edges are not recomputed. This is similar to the "Do not create" option above except that the gaps are filled with new faces.
Add Offset
Use this option to attach an offset attribute to a face.
The attribute will govern that face despite the Offset value specified
above. It allows you to control the wall thickness at selected faces independent
of the part's typical wall thickness. 
Select a face.
Specify the offset value. A negative value indicates an internal offset and positive value indicates an exterior offset.
Delete Offset
Use this option to delete an offset attribute created with
the Add Offset option above. Select the attribute(s)
to delete.
If you select a shell face to offset and it already has an offset attribute attached to it (i.e., you used the Add Offset option above) and it has not been applied yet, the offset attribute will be applied instead. The offset from this command will be logged into the part's history but will not go into effect unless the offset attribute is deleted and the part is regenerated.
This command could fail if the concave fillet is offset a distance that is larger than its radius.
