Bricks

Bricks are often used for building because they are strong, not only in the sense that they are not easily broken, but also in the sense that if they are staggered in this way then they will not break because they fit together well. They are useful for this purpose because they create the correct amount of total degrees. Rectangles, by definition, have four 90 degree angles. If you put two next to each other, then you will have 180 degrees, making a straight line, which has 180 degrees! Perfect!  ~CB1