Fixed Constraint
The Fixed Constraint node adds a condition that makes the geometric entity fixed (fully constrained); that is, the displacements and rotations are zero in all directions.
Face Defining the Local Orientations
This setting is used in conjunction with weak constraints. In order to be able to interpret the orientations of rotations to which the Lagrange multipliers are defined, you must know to which boundary they are applied. Select the boundary which should be used when setting up the weak constraints. The default is Use face with lowest number.
Constraint Settings
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.
In the COMSOL Multiphysics Reference Manual:
Location in User Interface
Context Menus
Ribbon
Physics tab with Shell selected:
Physics tab with Plate selected: