Found at Home Depot, Lowe's, your local home improvement shop or even online, the automatic gate latch, or sometimes called gravity latch, can be a simple answer to keeping your gate securely shut. Whether you are keeping pets and children in or other unwanted pests out, a good latch is often all you need. In minutes a self-locking latch can be installed that will last for years.
Line up your latch where you want it to be positioned on the fence. Hold the latch so the anchor, or lock, is resting on the stable post, and the latch arm is placed on the movable gate. Keep the latch toward the top so that it is easily reachable from either side to open it. Usually 1 to 2 inches from the top edge of the gate is sufficient to conceal it from view on one side and still have easy access.
When you are satisfied with the placement of the latch, mark the point where each of the screw holes will be. Set the latch arm down and hold the lock piece steady. Screw the lock piece to the gate post to secure it. The lock should be completely anchored to the post with no movement other than the lever mechanism.
Place the latch arm back against the gate, using the markings as your guide. With the latch arm through the lock, screw the arm to the gate door. Test your latch; it should open smoothly and lock smoothly each time with a simple push. If you are finding you have to force it to get the latch open, reposition the latch arm to relieve the tension.
Gates can sag over time. If desired, anti-sag kits are available and can lengthen the life of your gate and therefore your latch.