A brick is a block or a single unit of a kneaded clay with soil, sand and lime, or hardened concrete-fire material or air-dried, used in masonry construction. Lightweight bricks (also called "block light") are made from expanded clay aggregates. Burnt bricks are the most numerous type and are laid in courses and many models known as bonds, collectively known as masonry, and can be installed in various types of mortar to hold the bricks together to make a lasting structure.