i'm hanging a pre hung door after finishing and hanging the door, it sags creating a large gap at the top but the jamb is still plumb what gives? The steps i took are as follows: 1. Placed the jamb in the rough opening, marked where the hinges will fall. 2. I screwed shims to the wall (jamb side) checking plumb with a 6 ft level 3. Placed the jamb back in the opening and secured it using 2.5 inch screws checking for plumb on both the face and the side of the jamb. 4. Hung the door back on the jamb checking the gap and the swing prior to nailing the latch side. How do i adjust how the door sits against the jamb i need to tighten to top? You can see by the red arrows the gap is 2 or 3x's larger on the top then on the bottom.