The Single Suction Lifter is ideal for holding onto the hull of your boat. Used in the motor trade to pull out dents. *Powerful Suction created by closing the leaver. *Sticks to the hull and any smooth surface. The Double Suction Lifter also features: *The Articulated cups enable the lifter to attach to curved smooth surfaces like a boat's Hull. *Sturdy Handle. *Powerful Suction.