In the reading, Ching talks about concrete, masonry, steel, stone, and wood. Different materials have different units and precast forms for easier and safer usage. Concrete, for example, consists of cement, water, and aggregate. It can be done on site, but for it to be sturdy and functioning, it needs steel reinforcement. steel reinforcement must be tied with both, vertical and horizontal elements to minimize shrinkage, cracks and control thermal expansion and contraction. Steel comes from the manufacturer in precast shapes. W, S, C, L, WT, structural tubings (circular, square or rectangular) and bars. Brick is a masonry unit of clay formed into a rectangular prism, same as stone there are different types of bricks and they are soft mud, sand bricks, water struck brick, stiff mud, and dry press.