Symmetry
Use the Symmetry node to add a boundary condition that represents symmetry in the geometry and in the loads. A symmetry condition is free in the plane and fixed in the out-of-plane direction.
Shell Properties
The selection in this section only acts as a filter for the boundary selection.The constraint is applied all through the thickness of the shell.
All other settings for the Symmetry node are described in the documentation for Symmetry in the Solid Mechanics interface.
Location in User Interface
Context Menus
Ribbon
Physics tab with Layered Shell selected: