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Inspect your fence for splits or small cracks. Apply a waterproof wood glue to these areas and tape it together for 24 hours while the glue dries. After a day, remove the tape and monitor the area for signs of further deterioration. Dig a hole around the base of the fence post approximately 1–2 feet (0.30–0.61 m) deep, depending on the size of the concrete spur. Place a concrete spur into each hole and attach it with bolts to keep it in place. concrete and fill the rest of the post hole to keep the spur from slipping over time.  A concrete spur is a long, thin concrete block used to repair broken or rotting fence posts. You can purchase them online or from most home improvement stores. If any of the wood is rotten, saw that area off and coat it with a wood sealant. If any screws or nails loosen over time, remove and replace them with stainless steel screws. To keep the screws in place, fill the tops of the holes with caulk. For further protection, look for weather-resistant screws online or at home improvement stores. Dip a bristle brush into wood preservative and lightly coat the posts around the base. This will prevent the bases from rotting and causing significant damage to the fence. If you live a humid climate or location with plenty of rainfall, apply wood preservative to all of the fence posts.
Use glue to fix minor damage. Reinforce significantly damaged posts with a concrete spur. Check for and tighten loose boards. Apply wood preservative to the base posts.