When replacing a fence, we set new posts in concrete. Because of moisture in the posts, bright sunshine and a time delay after putting up the posts, some of them warped slightly.
Before installing the rails and upright boards, pulling the posts plumb again became somewhat of a challenge, as I had no block and tackle or come-along. I wrapped a nylon strap (rope or wire would do just as well) around the post tops, and then used a long stick to provide the force to complete what I’ve heard called a Spanish Windlass.
Twisting the looped nylon strap with the stick pulled the posts into perfect alignment. By clamping a pipe clamp to one of the posts, I was able to lock the stick in place after twisting it and then nail the upper rails in position.
Santa Cruz, California