Rivets, bolts, screws and special bonding adhesives are used to hold the sheet metal in place. Regardless of the method of attachment of the material, every part of the fuselage must carry a load, or resist a stress placed on it. Design of interior supporting and forming pieces, and the outside metal skin all have a role to play in assuring an overall safe structure capable of withstanding expected loads and stresses. Engineers carefully calculate the stress a particular part must withstand. Also, the material a part is made from is extremely important and is selected by designers based on its known properties.
Aluminum alloy is the primary material for the exterior skin on modern aircraft.
This material possesses a good strength to weight ratio, is easy to form, resists corrosion, and is relatively inexpensive. Fittings must be made of carefully selected materials because of their importance of holding the aircraft together under expected stress and loading. The same holds true for important fasteners such as bolts and rivets. It is essential that these parts not fail under stress. It is also essential that these parts not weaken with exposure to stress and weather elements.