Bottom weighted mats have more width at the bottom than on the top and sides. This technique is most often used
by professional photographers and artists who prefer a "museum" type look. It also helps to counteract a visual
perception problem. If a picture is placed directly in the center of a mat with equal width borders, the human
eye will perceive that the picture sits below center and therefore look top-heavy. A weighted mat compensates
for this illusion and better balances the presentation.