A composite 2D region may be used in exactly the same way as a primitive 2D region to define the location of a Boundary Condition, Domain Interface, and so on, in the model.

A composite 3D region may be used in exactly the same way as a primitive 3D region to define the location of a Domain or Sub-domain in the model.

Mixed-dimensionality composite regions can be used as locators, but only the primitive regions of appropriate dimensionality are used in the location. For example, a mixed-dimensionality region used as the location of a boundary condition will mean that the boundary condition is defined only on the 2D components.