I made two wood wheel ramps to use to get my coach high enough to get under to work on. I'm posting this because someone was asking what I use.
It was pretty easy and cheap. I bought one sheet of plywood and two 2"x6" x 8 ft boards (8" wide would have been better). I used decking screws to tie it all together.
Two strips of 2x per side (one board center under each of the dually tires.
This gives me plenty of height to get under coach even with air bags dumped.
The ramps are pretty heavy (probably 40 lbs each) - I added "hand holds" to help move them but I should have left more wood between the edge of plywood and the cutout, because one of the holds already broke.
The four 2x and plywood sandwich gives about 8" of lift. These are heavy enough and the ramp angle is gradual enough that they don't slide or slip out of place while driving up on them.
I should also add that I have 20T jack stands that I would use if I was to pull a tire, but for just getting under the coach, this is all I use.
