The installation is done the same way, you have to head off the joists in makng a rough opening. Assuming you need a rough opening of 54" length you will cut off 3-joists (24" O.C.) and frame doubled headers between the uncut joists at eigher end. If you are installing in a hallway, the walls on either side may serve to support joists while you cut and frame. If span is open, you must support cut joists. Can you describe the installation?