The Subdivider Orientation dialog box appears on your display whenever the Add Subdivider command is selected and there are presently no subdivision lines in your circuit. This dialog box allows you to select an orientation for all your subdivision lines. You may choose between Horizontal or Vertical. All the subdivision lines in a circuit must share the same orientation.
If you wish to use both orientations, you may perform a "double" subdivide. Subdivide your circuit using one of the subdivision line orientations. Then, you may subdivide the resulting geometry subprojects using the opposite orientation for the subdivision lines.