This tool, by Japanese manufacturer Nissin Boeki, is for resizing cardboard boxes. (If you've ever done this yourself, you know this is typically an inelegant process.) I find the design fascinating.
There's an adjustable slider on the shaft. You'll use this as a "fence," after locking it to the desired height.
The wheel on the bottom has little teeth.
Perhaps now you can guess how it works, and so you just clicked away, which is fine; I get paid whether you read to the bottom or not so it's your loss. Those who stayed get to enjoy these images below.
With the fence riding on an edge, you slide the tool horizontally, and the wheel scores a line across the surface.
You then use a boxcutter to slit the four corners down to the score line. Fold at the lines, and boom, smaller box.