Sometimes, you do not want all surfaces of a part model to be shelled. For example, you may not want the grips in the upper-right figure to be shelled. You can exclude surfaces from the Shell feature. Excluding surfaces enables you to select one or more surfaces and exclude them from the Shell feature. In the lower-left figure, surfaces are selected to be excluded from the shell. In the lower-right figure the shell has been completed, and the grips are not shelled.
When specifying surfaces for exclusion, you can open the Surface Sets dialog box. The Surface Sets dialog box enables you to further add Individual Surfaces, Seed and Boundary Surfaces, and Excluded Surfaces.