Use straight-grained American elm or oak, the former for preference. After being shaped and dressed, the ribs are steamed or soaked in boiling water till pliable, and bent over the knee where necessary. The ribs on either side are notched to fit over the keelson, and butt against each other where they cannot be carried right across. The keelson must not be cut; the ribs are usually spaced closer in the bow to add strength. Floor ribs extending on either side of the keelson and between the others are also notched and fitted over the keelson. A fore and aft stringer on either side is then screwed to both sets of ribs, which bind the whole together.