Shell Solid
Insert
Shell/Offset
Use this command to create an offset shell
feature from a shape. The offset will apply to all faces of the shape
except those that have offset attributes. Optional inputs include the
ability to keep the original shape, attaching and deleting offset attributes
to individual faces, removing self intersecting faces and assigning a
unique name to the feature if desired.
Shape - Select the shape to shell.
Thickness - Specify the shell thickness. A negative value indicates an internal offset. A positive value indicates an external offset.
Openings - Select which faces if any should be deleted from offset consideration or middle-click to skip this option. These faces will reside in the new feature but will not be offset.
Create side faces
Check this box to create any required side faces during the offset to maintain a closed solid. In most cases, this only applies to open edges. If this box is not checked, open edges will remain so.
Intersections
Use this option to remove self intersecting faces. This option
will also detect disappearing face fillet, fillet corners, and chamfers.
These options require some time to complete depending on part complexity.
Do not remove - Ignore self intersecting faces.
Remove fast - Limited to removing self intersections on or near faces that become completely inverted, such as a fillet that is offset more than its radius. Anything beyond this is not handled.
Remove all - Remove self intersections and inverted regions (including inverted inner loop cases) as well as can be done. Faces that intersect other faces in the shape will be split.
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 offset thickness is larger than the radius of the smallest concave fillet on the shape.
