To level a fifth wheel trailer, such as a Keystone Montana, use plastic leveling blocks, wooden planks or inflatable levelers to level side-to-side first, and then front-to-back. After leveling side-to-side, check the leveling with a level before checking the front-to-back leveling. Unhitch the trailer when both sides are level within a half inch of the opposite side.
As the trailer comes into the area where it must sit, take a level check before anything else. Check the side-to-side level first to determine if one side or the other needs to rise. If one side needs to rise, place the leveling material onto the ground, and then pull the trailer on top of it before checking the levels again. This may take a couple of tries before getting the trailer level. At this point, chock the wheels, and prepare the trailer for unhitching.
Before unhitching, ensure the front-to-back levels are also even. If the front is too low, use blocks under the landing gear, but if it is too high, extend the landing gear before unhitching. When it comes time to unhitch, raise or lower the landing gear to reach the front-to-back level, and then lower the stabilizer jacks. Remember, the stabilizer jacks are not meant to carry the weight of the trailer, only to reduce the amount of shaking.