The spacing of the holes prevents the top plate from being mounted incorrectly. However on a couple of the generic replacement senders the beam (the beam that holds the sending unit) is capable of being attached in 4 separate orientations. The original sender was a stamped little rectangle (you can see it in my image) but some of the generic replacements aren't...the stamped recess is square and that means the float rod might be trying to operate 90 degrees out of the intended spot. Somewhere I kept one that came to me that way.
