Guards

Also paddle guards and wheel guards.
1. (on an oceangoing sidewheel steamship) Horizontal structures, usually of wood, built around the paddle boxes just above their lowest point and extending a short distance forward and aft, designed to protect them from damage and to provide additional support for the paddle shaft.
2. (on an American sidewheel steamboat) Extensions of the main deck beyond the hull to the outer extremity of the paddle boxes, and tapering to the bow and stern (thus giving the deck a characteristic oval shape), to increase the available deck space for passengers, cargo, and/or machinery.