This chapter describes the raw materials, manufacture and properties of the components of masonry, that is, the various brick and block units and the mortar that bonds them in the final structure. It will be apparent that there is some overlap with the descriptions of cement and concrete. The chapter describes the shape types and terminology of masonry units. They are mortar, binder, work size, coordinating size. Many organic compounds improve plasticity, or workability, of mortars, rendering mortars, infilling grouts and concrete used for manufacture of units. In a finely ground state, chalk is used as a filler and plasticity aid in masonry cement and some grouts. Masonry walls require openings for doors, windows and services. The main intended uses of these units are facing or exposed masonry in load-bearing or non-load-bearing building applications. Joint reinforcement is also used to resist out-of-plane loading and to tie masonry together, particularly to resist accidental damage such as earthquake-induced failures.