Foam neoprene gasket which fits between the upper and lower parts of the Topper deck at the daggerboard slot. To fit this piece you will need to take off the hull plate from underneath and remove the daggerboard moudings. Then turn the boat over and remove the selfbailer unscrew the daggerboard screws from the top of the deck and the centremain fixing (if it is a centremain boat). This will enable you to prise the upper and lower parts of the deck apart to remove the old gasket and insert the new one. When this is complete you can then reattach all items.