Abstract: An elongate channel insert configured for installation between elongate structural members to prevent water from flowing through an overlying structure into the area beneath the structural members includes a U-shaped hook on a first side of the insert that goes over the top and both sides of a joist, an L-shaped ledge on the other side of the channel insert prevents the inserts from becoming off center as they are placed side by side on joists across the entire width of a deck with the base of the insert angled along its length such that water captured within the channel will drain from one end of the insert to the other.