Which type of seal creates a protective cover over fasteners such as rivets and bolts that protrude above a surface?

A cap seal is specifically designed to create a protective cover over fasteners such as rivets and bolts that extend above a surface. This type of seal effectively prevents contaminants from entering and protects the fasteners from corrosion and other environmental factors. By enclosing the exposed parts, cap seals help maintain the integrity of the fastening system, which is crucial for ensuring structural reliability and longevity in aerospace assemblies.

In contrast, sealants are typically used to create a seal between surfaces to prevent leaks, while washers serve to distribute the load of a fastener and protect the surface beneath it. Gaskets provide a sealing surface between two mating parts but are not designed to cover protruding fasteners. Each of these components plays a distinct role in assembly and maintenance, but the cap seal's primary function in covering fasteners makes it the correct choice in this context.