Paper cutters are precise tools for slicing paper, with one minor deficiency: You can't always see where the blade will cut. For some models, you can fix this by shining a light beneath the paper.
As reddit user VolcanoHoliday points out in the photo above, by shining a light below the paper, you can see exactly where the edge of a paper cutter ends and thus where the blade will cut. Unfortunately, this only works on larger paper cutters like this one where the blade drops to cut along the edge. Smaller paper cutters like this one where a smaller blade slides along the paper don't have a drop off edge that you can shine a light behind. However, if you have to use one of those larger paper cutters regularly, mounting a light could help you be more precise.