Extreme wind, vehicles and water damage over time can all cause wooden fence posts to break. Whether the post breaks partway up or at the base, it needs to be completely replaced to maintain the fence's integrity and stability.
If the wooden post is not secured below the ground by cement, drill or dig beside the pole to release it. Builders usually bury posts about 2 feet below ground level.
Drilling Out Cement
A large concrete plug usually secures wooden fence posts below the ground, making drilling out the post nearly impossible without a jackhammer. Even if the post is somehow removed leaving the hole in the cement intact, the old cement will not hold a new post securely. Drilling out is possible but not a feasible solution.
Cutting off the worn post is a better solution. Dig down below the ground level and cut off the post with a saw. Then place new posts about 2 feet on each side of the old post along the fence line, and put in new rails to fit.