Bricks are typically made of clay and shale, but they can also be made of concrete, sand and lime. Normally, the material is kneaded to thoroughly mix it and is then heated to dry it. Some of this drying occurs in the sun or in special ovens.
Molds are used to keep the bricks a uniform size as they dry. The molds are bigger than the final size due to the shrinkage that occurs during the drying process. This is important when the bricks are used in construction to make sure that the right amount of materials is bought. It also affects the final appearance of any project if the bricks are not all the same size.