The Ironwood Pacific Top-Snapper is designed to make fastening your boat canvas easy. If you are inside the boat, simply grab the inside of the snap with the Top-Snapper, align the 2 halves of the snap, and pull it closed from inside the boat. If you are outside the boat cabin, simply slide the Top-Snapper under the snap cap, align the 2 snap halves, and press the snap together.