What is the piece of steel used to support masonry units over openings called?

A piece of steel used to support masonry units over openings is called a lintel. Lintels are crucial structural components, as they carry the load from the masonry above the opening—such as doors and windows—distributing that weight down to the sides where it can be properly supported by the structural walls.

In masonry construction, the lintel is positioned horizontally above the opening, ensuring stability and preventing sagging or cracking in the masonry surrounding it. This is particularly important because masonry, while strong in compression, can be weak in tension or flexure without proper support.

The other terms relate to different structural elements but do not serve the same specific function as a lintel. A beam generally spans large openings and supports overhead loads but is typically broader in application and may require more complex calculations for load-bearing. A post acts vertically as support, often for beams or trusses, while a truss refers to a triangulated frame used to support roofs or other structural elements over larger spans. Thus, the lintel specifically fulfills the need for supporting masonry above openings.