Bricks are rectangular blocks made from clay that are hardened through firing in a kiln. They have been used in construction for thousands of years due to their durability, strength, and versatility. Good brick material contains 20-30% alumina, 50-60% silica, up to 5% lime, and 5-6% iron oxide to impart strength, prevent cracking, and determine color. Bricks are manufactured by removing topsoil, blending clay with additives, tempering the clay with water, and forming rectangular blocks.