Localized area of extra layers of reinforcement, usually to provide stiffness or strength for fastening or other abrupt load transfers.
A second sheet of material fixed inside {or sometimes outside) the main fuselage side sheets on each side for added strength.
additional plate welded on top of the original plate to increase stiffness or local strength; in some cases to maintain watertightness
Extra balsa or plywood added to the fuselage sides for added strength.
a wood or metal plate bolted beneath a mounting surface for reinforcement.
a second piece of balsa or plywood added to the fuselage side to enhance strength.