works great anywhere you need to remove a nail from a siding. So when you arrive at the top of a wall or under a large window, simply install a finishing strip (also known as a snap strip) inside the J-Channel. Then cut the fairing long enough to fit inside the fairing. After that, go back and iron the top of the trimmed trim every 4-6 inches. This tool makes a directional notch in the panel that allows it to snap into the snap-on panel. No exposed fasteners are required to attach the top wall or any other place where you need to cut the top of the trim.