It is crucial for all pages in your paper stack to be evenly aligned before cutting in a stack cutter. The easiest and most efficient way to do that is with a jogging block. They slide easily on the surface of your stack cutter, tamp the pages flat and straight, and help you provide the cleanest cuts you can. It's well worth the investment so you don't have to rely on hand tamping, that is more dangerous, and takes much more time. A jogging block is a necessary addition to your stack cutter.