The Reinforced Bead Elbow fits in the system at the bottom of the downspout. The bottom lip is gently curled back, making the end smooth and gentle to the touch, keeping the smallest of persons and their curiosity in mind, no risk for cuts. The top is expanded to fit outside the large end of the downspout, should you have cut it to use the pre-shrunk end. To fix the RBE to the downspout, put a small tap screw in the back of the product. This is actually the only screw, you ever put into the system.