A control joint bead is a manufactured element, installed within plaster, stucco, or concrete surfaces to form a deliberate gap or groove known as a control joint. This bead provides a clean, defined line where the material can crack or move in a controlled way, managing stresses caused by shrinkage, thermal expansion, contraction, or structural movement. Control joints help prevent unpredictable and unsightly cracks by directing where they occur, thus preserving the durability and visual appearance of the surface.