Shell Command

            You can create a shell or a hollow thin wall with a specific thickness from your 3D solid object. AUTOCAD creates new faces by offsetting existing ones inside or outside their original positions. AutoCAD treats continously tangent faces as single faces when offsetting.

1. Choose           Modify, Solid Editing, Shell
2. Select             a 3D solid: pick solid
3. Remove         faces or [Undo/Add/All]: enter
4. Enter             the shell offset distance: 0.5