Over time, your wooden gate may begin to sag. The latch no longer operates properly and the gate begins to drag on the ground, making it difficult to open and close. The most common reason for a sagging gate is that the gate frame has become warped and gate's joints have loosened. The answer is an anti-sag gate-repair kit. The simplest anti-sag kits include two screw hooks or eye screws, steel cable, a turnbuckle and two cable clamps. Without removing the gate from the post, you can re-square the gate frame so the gate no longer sags and the latch operates properly.
Close the gate. Place scrap lumber under the stile (the vertical framing member) on the latch side of the gate to raise the gate until the latch is aligned to function properly.
Drill pilot holes into the inner surfaces of the stiles of the gate frame, one near the top rail of the hinge side and another near the bottom rail of the latch side. Make sure that the drill bit is slightly smaller in diameter than the threaded shanks of the screw hooks included in the anti-sag kit. Screw a screw hook into each pilot hole until their curved portions meet the frame.
Turn the eye-screws on the ends of the turnbuckle so the turnbuckle is fully expanded. Place a cable clamp on one end of the cable. Thread the end of the cable through one eye-screw on the turnbuckle, then back through the cable clamp. Use a screwdriver to tighten the clamp onto the cable. Hook the eye-screw of the other end of the turnbuckle onto the screw hook on the hinge side of the gate.
Place the second cable clamp onto the other end of the cable. Thread the free end of the cable through the screw hook on the latch side of the gate, then back through the cable clamp. Pull the free end of the cable until the portion of cable between the screw hooks is taut. Slide the cable clamp as close as possible to the screw hook. Tighten the cable clamp. Use wire-cutting pliers to trim excess cable.
Tighten the cable between the hooks by turning the turnbuckle clockwise with an adjustable wrench. Watch the latch as you tighten the turnbuckle. When you see the latch side of the gate begin to rise and the latch pieces line up, the cable is sufficiently tightened. Remove the scrap lumber.
Some manufacturers include specialised mounting brackets to attach the cable to the gate frame. The brackets are screwed to the frame before attaching the cable.