This slide rule works the same way as the slide rule for adding numbers. Double-click the button to see the actual distances that are being added. for example, look at the numbers on the slide rule and the actual distances that are being added for the multiplication 2 x 4 = 8. This becomes the addition 1 + 2 = 3. It works because
See the slide rule for adding positive whole numbers for a clearer idea of how it works.