Since people first began putting windows in their shelters, they have needed a way to support the weight of the wall above the window. The solution was the lintel, a beam that spans from one side of the window to the other. Masonry lintels must be reinforced. They can be constructed of standard clay masonry units (solid or hollow), glazed brick and tile, specially formed concrete masonry lintel units, bond beam concrete masonry units, or standard concrete masonry units with grooved, depressed, or cutout webs. These units are laid in a masonry wall in a way that creates a channel in which steel reinforcing and grout are placed. DETERMINING THE LOADS To design a masonry lintel, you must first determine the load to be supported. The Brick Institute of America (BIA), National Concrete Masonry Association (NCMA), and authors Schneider and Dickey in their book, Reinforced Masonry Design, all use a graphic load diagram to do this. In this method, the lintel is designed to support a triangular section of masonry above it. Outside this triangle, arching action of the masonry is assumed to support the weight of the wall and any uniform loads, such as roof trusses or floor joists.