There’s usually more than one way to do a job, and installing prehung interior doors is no exception. I’ve developed a systematic approach that ensures an efficient, durable, topnotch installation. It takes me about 30 minutes on average to install a prehung door and another 20 minutes to trim it out — handy information when giving a quote.

First, I prep the opening by trimming drywall edges back to the studs and hammering any high-riding fasteners flush. To make sure the jack and trimmer studs don’t move as they dry, I supplement the framing nails with 3-inch screws. I check the floor for level across the opening (1) and along the door’s swing arc (2), noting any deviation in...

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