Move the outer two arms of the calipers and note how the third arm stays at a proportionate distance between the two outer arms. The shorter of the two distances (a) is proportionate to the greater of the two distances (b) in the same ratio that the greater of the two distances (b) is to the sum of both (c). So "a" is to "b" as "b" is to "a+b" or "c."
Use the calipers to measure small objects. Hold the calipers against a small object, photo or drawing in a book and move the two outer arms so they point at major elements such as the edges of the object or photo. If the third arm points to a major design element—a border or framed part—perhaps you are looking at something designed with the golden ratio. Try flipping the calipers around, vertically and horizontally, to repeat this step and see whether this is correct.
Use the calipers to measure large objects. Even though your calipers might be small, they can be used to determine whether large objects such as buildings, large paintings or bridges follow the golden mean. Hold the calipers at a distance from you with the large object in the background. Adjust the outer arms to point at major design elements such as the top and bottom of the building in the distance. If the middle arm points directly to a major or unique design element, then perhaps the object follows the golden mean. Repeat this step with other major design shapes of the object such as frames, borders or columns to see whether this is correct.
Use the calipers to create something new. Use your calipers to help frame out projects such as drawings, furniture designs, home remodeling projects, even photos. As you are composing plans for something new, try using your calipers to add a pleasing visual proportion—the golden mean—to the design. You will be helping to continue an artistic element found in nature and art throughout history.