A joist is a horizontal structural element used in construction to support a ceiling or floor. Typically made from wood, steel, or engineered materials, joists are spaced at regular intervals to distribute weight evenly and provide stability. They play a crucial role in the overall integrity of a building's framework. In residential and commercial buildings, joists are often found in the framework of floors and ceilings. They work in conjunction with other components, such as beams and trusses, to create a strong and durable structure. Proper installation and spacing of joists are essential for safety and performance.