Part Modeling > Engineering Features > Shell > To Create a Shell Feature by Excluding Surfaces
  
To Create a Shell Feature by Excluding Surfaces
1. Click Model > Shell. The Shell tab opens.
2. To remove surfaces during the Shell feature creation, click the References tab, click the Removed surfaces collector, and select one or more surfaces.
 
* You can also select one or more surfaces to remove before you enter the Shell tool.
3. To modify the shell thickness, type or select a value in the Thickness box on the Shell tab. You can also drag the handle or double-click the thickness value and type or select the new value.
4. To exclude surfaces from being shelled, click the Options tab, and click the Excluded Surfaces collector, and select one or more surfaces to exclude from the shell. Alternatively, use the Exclude Surfaces command on the shortcut menu.
5. To specify the surface extension type, select one of the following on the Options tab under Surfaces Extension:
Extend inner surfaces—Extends the inner surface of the shell.
Extend excluded surfaces—Extends the excluded surface of the shell.
6. To prevent the shell from cutting through the solid at concave corners, select Concave corners on the Options tab.
7. To prevent the shell from cutting through the solid at convex corners, click the Options tab and select Convex corners.
8. Click .