Install a Split-Jamb Door Plumb, With a Perfect Casing Reveal

The Problem

A split-jamb door's casing is already attached to both jamb halves, which is its selling point — no separate trim day — but it means every plumb and reveal decision happens while you're holding an assembled unit that, in the creator's words, keeps trying to walk out of the opening.

The Technique

1. Pull the shipping staples and separate the two jamb halves.
2. Remove the plastic latch keeper from the strike area before the door goes all the way in, so the door can actually open once it's set.
3. Set the hinge-side half in the opening. Hold it there with a door jack under the unit if you have one — shims under the door work too.
4. Shim above the head jamb on both sides. That top shimming leaves a little play to correct either side if it proves out of plumb.
5. Stand a laser level at the top of the door and check the hinge jamb plumb top to bottom.
6. Shim behind each hinge. At one hinge, swap a short factory screw for a longer screw of matching head — driving it pulls the jamb toward the framing, and you shim to that pulled-plumb position and snug it a hair more.
7. Move to the other side of the wall and slide the second jamb half into the first. Set the laser as a reveal reference, hold the casing flush to it, and nail through into the jack studs — that keeps the reveal consistent the full height.
8. Shim the latch side in three places, then nail off the casing all the way around on both sides.