A large rectangular brick used in construction for the load-bearing walls of buildings. Suburban houses typically employ a concrete foundation and slab with a concrete block wall on the perimeter. Cinder blocks are made from coal cinders and portland cement. They are formed typically in the shape of two squares joined on one side to form a rectangle, with the insides of the squares hollow. This allows structures to be built in the traditional masonry style of overlapping rows, with the structure's weight carried by the "walls" of the blocks.