For a model element, the surface setting depends on its Building Material, which includes a surface.
See Building Materials.
However, for any model element, you can override the Building Material surface definition, and assign a different surface (or surfaces).
GDL objects do not use Building Materials, but you can override their surface definitions.
There are two workflows for overriding an element surface:
•Use the Surface Painter palette (See Override Surfaces With Surface Painter)
•Use Element Settings as follows:
1.Select a placed element, or open the Default Settings dialog box for the element type.
Note: Clicking the Chain icon (“Link Surfaces”) means that all of faces/edges will use a single surface override. To set a separate surface for any single face/edge, unlink the surface definitions by clicking the chain again.
To remove an override, just click the toggle button again. The surface defined in the Building Material is now used again.