In this "Fetch!" activity, you will build a two-story building for Ruff out of index cards, using just one shape - a square, an arch, or a triangle. The material that a building is made from (wood, concrete, brick, or steel) affects how strong and stable it is. But the shapes used to build a structure also help the structure support weight. In this activity, you will test three commonly used architectural shapes: arches, squares, and triangles, to determine which is the strongest. Once you've tried using different materials, you'll know which shape is the strongest of them all!