Shell outward means the thickness addition is from the outside edge and direction away from that surface.Shell inward is just the opposite of the shell outward one. Also you can decide whether shell outward or shell inward. Multi-thickness shelling helps you to apply different thickness on the faces as per your design need.
Here, both uniform thickness and multi-thickness shelling can be easily done by using this feature tool. In Solidworks, Shell feature having their own property manager which controls the application of shelling process on designed models. The Solidworks shell tool is located in both features commandmanager and Insert menubar. Checkout Best SolidWorks Training Materials here. It is also a placed feature tool which can apply directly on the existing model or features. Using this tool, you can make either completely closed hollowed model or one face opened type. SolidWorks shell tool is mainly used for shelling process, in which the material removed from the inner body of model by keeping small thickness and results a hollow model.
Also, it explains the Shell features and its uses in Solidworks CAD modeling. Welcome to Solidworks tutorial for beginners and in this tutorial post, you are going to see how to use the Solidworks shell tool feature in this CAD software in step by step manner.