Weifa double J control joint is engineered to prevent cracking in stucco and plaster surfaces by providing a space for expansion and contraction. To install, align the control joint vertically or horizontally on the wall, depending on your project's requirements. Attach the control joint using appropriate fasteners, ensuring that it is properly aligned and level. Apply the stucco or plaster mix to either side of the control joint, allowing for sufficient space for expansion and contraction.