The Boundary Layers node () can only be used for features that represents a boundary condition, using the boundaries of that feature. The domain selection can be specified in the Domain Selection section in the same way as other selection sections in the Physics Builder.

This section contains settings for setting up the boundary layers in the same way as the Boundary Layers feature under the meshing sequence. The fields in this section for Number of boundary layers, Boundary stretching factor, and Thickness adjustment or Thickness — depending of if Thickness of first layer is set to Automatic or Manual — accept the same builder parser syntax as the expression fields in the Usage Condition nodes. The most important syntax limitation for that context is that no variables are allowed in the expression, and some fields must be evaluated to a integer or number. If the value comes from a user input, that input must then do proper syntax check.