When we check level, we put bubble level on counter near fridge. Recently put on floor & noticed a difference. Where do most people check? Counter is a lot earlier.
I bought a couple of these and leveled the MH at home using a long carpenters level on the floor. Then I put one of the purchased levels on the driver's door and the other on the face of the dash with them also level.
Now, I can just sit in the driver's seat and use them to get the MH level in both directions.