Shell Solid

(3D only) Used to create a hollowed out solid having faces of a defined thickness. One or more selected faces may be removed to create an opening. You can shell both standard solids and those that have been modified in some way.

You can access this tool from the following:

Ribbon: Modeling > Solids > Features
Ribbon: Modeling > Home > Modify > Features
Toolbox: Solid Features

Setting	Description
Shell Thickness	Sets the wall thickness for the remaining faces.
Variable Link	Let's you use an existing variable to set the input value, defined in the Variables dialog. Note: If no variables exist, you will be alerted to create one first.
Shell Outward	If on, material is added to the outside; the original solid defines the inside of the walls.

Key-in: CONSTRUCT SHELL