Determining what constitutes “level” inside an imperfectly constructed RV is an interesting trick. We used a carpenter’s level on our kitchen floor, in several directions, and on our table, and on the bedroom floor. Of course, none agreed! But we found a good compromise and then mounted some RV levels on the outside of the rig to give us a reasonable guess when we’re setting up.
There are two different types of levels: Bubble Levels that have an air bubble that floats to the high side, and Ball Levels that have a ball that drops to the low side. Bubble levels are more responsive (the bubble moves more quickly as the RV moves). Ball levels take a few seconds to react. If you use both types, you can get confused because they move in opposite directions.
We have a large Level Master level on the fifth wheel pin box that is easy to see from inside the truck. We also have two small bubble levels on the trailer on the corner by the landing jack power button, one facing forward (for left to right leveling) and one facing sideways (for front to back leveling).
Our pin box mounted Level Master, a ball level, is easy to see from inside the truck. When the trailer is higher on one side than the other, the Level Master ball falls to the low side.
Our smaller levels on the front corner of the fifth wheel are bubble levels, so the one on the front of the rig showing the side-to-side level has a bubble that rises to the high side. This is the opposite of the ball level on the pin box, and sometimes, when we are struggling with white line fever from hours on the road, this messes us up.
I’d recommend sticking to either ball levels or bubble levels and not mixing and matching like we did! A good solution might be to mount a ball level like this on both the pin box and on the front of the trailer near the landing jack power button.
Why do you need two side-to-side levels? When I’m running around placing the boards in line with the wheels for Mark to drive onto, I want to see a level on the fiver easily myself, and the front of the pin box is impossible to see from the side of the truck when we’re hitched up.
However, lots of folks rely on a single pin box mounted level that has both side-to-side and forward-back levels in it. There are a few from Camco and Hopkins that are very popular.