ORIGINAL: SafariHummerH2

The left side of the ladder top mount flange has a larger area point for the screw hole which lines up exactly where the original top moulding plastic push plug is on the roof molding.
The right side of the ladder top mount flange has a smaller area point for a screw hole to be drilled out on the vehicles rear door. (which I did not do since I don't want to drill any holes on my vehicle)
However the ladder is very secure and sturdy.
The bottom screws just clamp on to the bottom of the door frame.
Although I knew that this was a left side mount ladder, I tried mounting it on the right side just to experiment, and discovered that the top mounting flange would not fit the top contour of the rear door. And the screw hole of the top moulding plastic push plug would not line up with the ladder.
As per the installations instructions, this hole must line up.
So this ladder is installed on the correct side (drivers side) as per the supplied instructions.