SENTRY fenders were designed to protect modern, low-profile, boats like runabouts, tow boats, and fishing boats. You can attach them to cleats, handrails, or dock pilings, and it will protect your boat both above and below the rub rail.Also, be sure to read the instructions included in the SENTRY box (little yellow booklet). Pushing down on the fender is key to getting the straps to lock in place. Pulling on the loose ends of the straps to the desired height is not enough. Push down to lock and pull up to unlock the straps.