Since we have different kind of trucks with low and high 5th wheels, and we never carry the same trailer. You will have times that the trailer is too low and you can not get under it. There are even times that the trailer is just a little low but has been sitting for a long time. You try to get under it and it rolls backwards and off the block. Then it falls and now sitting on the ground. How do you pick it back up?
There are a bunch of different way to get under the trailer after it has fallen or too low.
1st thing you will need to do is put air in the tanks of the trailer. Get as close as you can to the trailer and hook up your red line. Then push in the trailer breaks on your tractor. That will help get the tires locked to get under the trailer.
If the breaks are way out of adjustment then either re-adjust the brakes while the brakes are released(trailer brake pushed in) or put big hunks of wood behind the tires of the trailer so the trailer will not roll backwards.
Then you will line up like you are going to back under it. But don't go under yet. Drop your air on the truck. Just get the frame under it. Then lift the truck. As long as the trailer does not roll back it will lift the trailer a little for you to get wood under it. After your truck has lifted it and you have wood under the trailer. Drop your air in the truck again and you should be able to get your 5th wheel under the trailer. If not keep doing this until you can. You might even have to put wood on your frame of the truck and the trailer to lift a little higher.
That is lifting the trailer by the truck and the easiest way.