USS Constitution’s 1795 white oak keel, exposed during the ship’s 2015-2017 dry docking. Today, the ship’s below-the-waterline copper sheathing is replaced approximately every twenty years; the copper sheathing in the photo covers the false keel which is a protective wooden layer for the bottom of the keel. The dark angled line upper left is one of the keel’s four, twelve-foot scarf joints. Margherita M. Desy, Naval History & Heritage Command Detachment Boston.