Joists are horizontal structural components used in building construction to support floors and ceilings. They are typically made from wood, steel, or engineered materials and are spaced evenly apart to distribute weight. Joists help create a sturdy framework that allows for the installation of flooring materials, providing a level surface for living spaces. In addition to supporting weight, joists also play a crucial role in maintaining the overall stability of a structure. They work in conjunction with other elements like beams and trusses to ensure that loads are evenly distributed. Proper installation and spacing of joists are essential for safety and durability in any building project.