So I have a toposurface imported in FBX format from Revit 2010 into Max 2010. The only problem is it's for a 3D Rapid Print but the toposurface is flat. It has no depth. So i need to extrude it in Max. I select the editable mesh then open my modify panel, choose the faces and try to extrude. It does extrude but only the face, ie: it's hollow which doesn't work for Printing! Any help on how to accomplish this would be greatly appreciated. Thanks.