If you need to attach two pond liner sheets together to make a larger sheet, the process is called “seaming.” It is similar to the method you would use to patch a hole or tear in the liner and be done correctly to avoid leaks. Whether you are using PVC welding products or pond sealing tape, it is critical to follow the manufacturer’s instructions for the product. As a rule, you need to: 1. Lay the liner on a perfectly flat surface 2. Clean the pond liner edges with acetone to ensure good adhesion 3. You may want to draw a chalk line 4-6 inches from the liner edges to guide your overlap 4. Apply the seaming product’s primer or activator to both sides of the seam and allow it to cure for 10-15 minutes 5. Apply your sealer tape, if using 6. Overlap the liner edges by at least 4-6 inches and press the seam together 7. Use a brayer to burnish the seam and ensure smooth, flat adhesion with no air bubbles 8. Work slowly and carefully along the entire seam and allow it to cure completely before using