Plumb

A level is placed against two perpendicular sides of the post during installation to verify it is exactly vertical in both directions. Professional installers check plumb immediately after driving or setting each post, while correction is still straightforward.

Sometimes. A wood post that has leaned slightly due to soil movement can sometimes be pulled back with a come-along and re-tamped or re-concreted. A post lifted by frost heave typically needs to be reset — the existing post pulled and re-set at proper depth with correct footing.

A gate that swings open on its own almost always has a hinge post that is out of plumb — leaning away from the gate, which creates a gravity advantage that pulls the gate open. The permanent fix is to re-plumb and re-set the hinge post with a proper bell footing, not to fight the symptom with stronger spring hardware.