These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out. Cut a strip of cardboard that's about one inch by 11 inches. Gently bend the strip so that ...

These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out. Cut a strip of cardboard that's about one inch by 11 inches. Gently bend the strip so that ...