Wall of Iron uses CL for only Range (which in this case is a 5 ft. square in front of the Guardian), and Effect (Which is set at 5 ft. across, 10 ft. high).
Only other thing that needs addressing is the Reflex save if they push it over. That won't be necessary as it is general assumption the barrier will always be connected to the ground, as these constructs are meant to make a temporary bastion of defense, not a falling object. This is likely the reason no save is mentioned for this ability, and why it is only listed under Defensive Abilities.