Last year I used a random collection of wood, mostly 2x4 and 2x6, to help level my bus. They got the job done, kind of, but were a hassle to use. Improvement is on the to-do list for this year.
The interwebs offer various stacking block models from Lynx, Camco, and others. They look okay, and $3.21 each on the Lynx at Wal-Mart isn't so bad.. as long as there aren't many needed, which is unlikely if it's one or both of the duals that need to be blocked up. It does seem like they would sink easily in wet/soft soils too. That creates a double problem of being out of level and also having to pry the sunken block back out of the soil.
Last night I came across this blog post
proposing to cut squares from a horse stall mat. This seems like it would come out about half the cost of the Lynx blocks.
Any thoughts on leveling? I'm certain few of us (if any) have hydraulic levelers installed. And surely there are at least a few who like their sink and shower basin to fully drain, dislike sleeping with their head downhill, and prefer to cuddle the significant other on their own terms rather than the dictates of gravity.. Right?