farm jack (thats what they're called up here in Canada)... I think I have heard the name jack-all used before too. I guess they are similar to those old ratcheting car bumper jacks.
But anyway, I meant to say a bottle jack. The farm jacks are really only good for closing manual slideouts. I've done a few trailers at the local trailer park with my brother... he's actually the expert... or you could say he's the brains and I'm the muscle of the operation...
...but thats how we did them. the first one I did with him was 3 years (or canadian winters) ago and they stand more level than my house