Auto Restrain (Surface)
The Auto Restrain (Surface) 
option is a convenient shortcut for automatically applying default restraint boundary conditions on the external boundary for surface models. When the Auto Restrain (Surface) option is selected, the bottom and sides of the external boundary will be assigned XYZ restraints, and the top surface (ground surface) will have no restraints (i.e. free). When using this option, RS3 automatically determines the top surface (ground surface) of the model. If the results are not as expected, you may have to manually assign the desired boundary conditions with the Add Restraints/Displacements options (e.g. Restrain X, Restrain Y, etc.).
This option is intended for surface models with a free ground surface (e.g. slope models).
To apply auto restraints to a surface model:
- Select the Restraints workflow tab
- Select Auto Restrain (Surface) from the toolbar, the Restraints menu, or the Right-click menu and restraints will be automatically applied, as described above.
After using this shortcut you can manually customize the restraints if necessary using the Add Restraints/Displacements options (e.g. Restrain X, Restrain Y, etc.).