Either a bottom or a top AND 2. Either a front or a back. It is preferable to make the rest of the polygons in the group 'not specified'. If you give the same orientation to more than one polygon, the engine will give that orientation only to the first one it finds. To avoid contradictory cases, give each orientation to one polygon only.
Orientation defines the object space.
This will repeat the bitmap 2 across and 3 down to fill the polygon. This will avoid contradiction. You can change one, two, or all axis. Give a name to the track. A car or an airplane, traversing the same route repetitively.