Hang a Pre-Hung Door

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.

The Problem

A pre-hung door looks like it should be easy — the door's already on the jamb — but there are two things to get right at once: the frame has to be plumb so the door doesn't swing itself open or shut, and the gaps around the slab (the reveals) have to be even so it looks and closes right. Chasing both at the same time, adjusting everything everywhere, is how first-timers end up with a door that binds.

The Technique

Split the job into two separate problems, in order.

1. Hinge side first. Set the unit in the opening and shim the hinge jamb until it's dead plumb and straight — this side is the door's foundation, and nothing else gets decided until it's right. Get a shim behind each hinge location, so the jamb is solid exactly where the door's weight hangs.
2. Then the latch side. With the hinge jamb locked in, shim the latch-side jamb with one goal only: making the reveals around the door even. The hinge side set the geometry; this side is purely cosmetic tuning.
3. Heavy doors get a long screw. Pull one short screw from each hinge (or the top hinge at least) and replace it with a long screw that reaches through the jamb and shims into the framing. That's what prevents the slow sag that ends in a binding door years later.

A good rough opening makes all of this easier — plumb, square, and with room for shims. A bad one causes problems no shimming order fully fixes.