Layout > Using Layouts for 3D Design > About Creating References for 3D Design
  
About Creating References for 3D Design
You can use centerlines, center points, and coordinate systems as references to map 2D geometry and define the placement of a layout in the 3D environment. The entities are automatically tagged as public and are shared with a 3D design.
Use these 2D geometric entities to mark various types of references in a 3D design:
Centerline—Marks the center of cylindrical geometry and rotational symmetry.
Center point—Marks the center of cylindrical geometry and rotational symmetry.
Coordinate system—Marks the relative location and orientation of entities.