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That is not just a bumper jack, it is usually referred to as a "farm jack"..a very useful tool. It can be used as a jack, but it can also be used to pull your rig out of the mud..
It can be a bar clamp, pulling things together.
Given enough rope, chain or cable and a tree or big rock, and it will pull your vehicle out.. It is also great for tightening barb wire fences, and myriad chores.
My son had one, but in doing 3 or 4 free, "good neighbor' jobs for needy people, he left it on one job or the other, but nobody called him back to tell him they had the jack. So he no longer has one.
The many uses for a farm jack...
https://www.youtube.com/results?search_query=uses+of+the+farm+jack