This jamb is eased and bevelled. See our dimensional lumber section for more sizes of dressed lumber that can be used as jamb. Door Jamb is the square wood frame around the three sides of the door or four sides of a  window. The casing gets attached to the sides of the jamb. The jamb will come in various standard widths to accommodate the 2×4 or 2×6 walls plus the thickness of the drywall on each side of the wall. The door stop gets attached to the face of the jamb to prevent the door from swinging through the wrong way.