Bilge keels extend straight out from the hull at a 90-degree angle (see Figures 1 and 2 in the Introduction). Put one of the bilge keels up against the side of the boat so that it fits onto the side. If the bilge keel is too big, trim it until it fits well on the boat. Bend part of the bottom of the bilge keel outward, away from the boat. Do the same with the other bilge keel. Make sure that the portions bent away from the boat extend out about 5 cm. Use your ruler to get an exact measurement.