Careening (also known as "heaving down") is a method of gaining access to the hull of a sailing vessel without the use of a dry dock. It is used for cleaning or repairing the hull. Before ship's hulls were protected from marine growth by fastening copper sheets over the surface of the hull, fouling by this growth would seriously affect the sailing qualities of a ship, causing a large amount of drag.[1]: 164 As this growth was underwater, removing it was difficult. Beaching the vessel at high tide allowed the lower hull to be exposed for cleaning or repairs.