Fixed Constraint
Use the Fixed Constraint node to set all displacements on the selected geometric entity (boundary, edge, or point) to zero.
To constrain interfaces between the material layers, use Fixed Constraint, Interface.
Shell Properties
Select the layer or layers on which this constraint is to be used.
When Use all layers is not selected.
All other settings for the Fixed Constraint node are described in the documentation for Fixed Constraint in the Solid Mechanics interface.
Location in User Interface
Context Menus
Ribbon
Physics tab with Layered Shell selected: