I take back my other answers and offer these insights-
Each side has 7 matching different sizes, got that?
The left side has a hump in the middle - the right,
is flat. Do they work together, or are they 2 versions of a similar thing.
It can't be metal going thru it because of the wooden rollers on the bottom - unless it's really thin.
Am I on the right track????

It's a wagon jack - the bar sticks into the side of the wagon (horse drawn, by the way) and locks into the ratchets.