Plumb Rail Posts With Staged Carriage Bolts: Bolt, Check, Bolt Again

The Problem

A rail post has to end up plumb in two directions while carriage bolts — which want their holes drilled with the post already in position — lock it down. Drill both holes with the post leaning and the bolts faithfully preserve the lean.

The Technique

1. Tack the post with one structural screw, placed where a bolt hole will later land — the bolt erases the screw's hole, so the finished post shows no stray "face hole."
2. Drill and set the bottom carriage bolt first, snug but not final. Starting at the bottom makes the plumbing easier: the post pivots from a fixed base instead of swinging freely. Drive the bolt through with the sledge, run the nut down with a wrench.
3. Check plumb left-and-right — this is the two-person part: one below on the bolt, one above sighting the level — and hold it while drilling the second hole.
4. Set the second bolt. The post is now locked plumb side-to-side.
5. Shim before final tightening. Toward-the-house / away-from-the- house plumb gets corrected with shims behind the post, then the nuts get their final tightening against the shimmed position.

Working alone, the creator's suggestion is a site-built jig to hold the post where the second person would — the sequence stays the same.