Stand the prehung door and jamb inside the opening. Tap some thin wedges between the jamb and rough opening. Cedar works well for this purpose. Use a variety of thicknesses, doubling them up if you need to. Use a level with the wedges to plumb the hinge-side jamb, tapping the wedges ...
The rough opening (RO) size refers to the frame dimensions to which the window attaches. "It's the original stick framing of that house, the opening that the window is supposed to fit in," says Andrew Prchal, president and co-founder of Gunner. The frame includes a header at the top,...