[wingnut60]

The problem is you have to have enought height on the front of the trailer to allow the entire jack column to be lowered below the bottom of the trailer and be moved sideways. Just jacking the front up is usually not high enough--a hole needs to be dug directly below each jack after the trailer is supported by other means--usually jack stands placed under the frames--that way the entire jack assembly can be lowered from out under the trailer frame. I haven't actually had to do this, but have seen some pics of others and you need a lot of space between the trailer and the ground--thus the hole.
Joe