| This is the ancestor of the modern day food processor. It provided a safer and more convenient way to slice food than by using a knife.
The Germans tended to call this a cabbage slicer (for making sauerkraut), since that is what they used it for primarily. Other nationalities called it other things, such as 'potato slicer'.
No matter what the vegetable that was to be sliced, this tool made the work more safe, cut down on the time it took to slice a whole vegetable and guaranteed that all of the slices would be the same. The size (i.e.thickness) of the slice could be adjusted. The thumbscrew on the side would be loosened and the panel to which the blade was attached could be adjusted, making the opening larger or smaller as desired. It might be noticed that there are 'side boards' to either help the user guide the food item to be sliced in line or to keep any liquid produced in the cutting process from splashing in all directions. The large opening on the opposite side allowed the slices to fall through easily. The tool would perhaps be placed overtop a large bowl in order to catch the slices.