Available with 3D Analyst license.
You can symbolize line features as 3D simple lines or 3D textured lines. Use 3D Simple Line to symbolize lines as 3D geometric shapes, such as tubes and walls. Use 3D Texture Line to turn your line work into realistic roads, fences, or walkways. The Symbol Property Editor is a useful dialog box for changing your symbol type and its associated symbol layer properties.
ArcScene does not honor 3D line symbols at version 9.2 or earlier.