a clamp for fiberglass boats is adjustable where the contact points are on any of the fiberglass hull , the fiberglass deck , and / or the fiberglass gunwale . the clamp has an outer jaw for contacting the hull below the rub rail , and inner jaw that is reached over and around the gunwale for contacting the deck inside the gunwale , an optional auxiliary jaw for contacting the outside of the gunwale , and an optional stand - off resting on the crown of the gunwale . preferably the jaws and stand - off are the terminations of linkages which can be re - configured in an indefinite variety of re - configurations .