The ONLY way to repair once and forget it is to use a piece of ripstop and Seam Grip. Round corners on patch, apply Seam Grip to fly and to uncoated side of ripstop. It will be stronger than the original material. Be sure and coat both sides of patch and when dry sprinkle on some unscented powder to keep it from sticking to itself. I always patch the inside of the fly. TMHO FWIW. If its silnylon use the stuff from Gear Aid/McNett for that material.