A cap nut, also called a dome nut or acorn nut, is a mechanical component that shields the exposed threads of a bolt or screw. Think of it as a protective covering that encases the pointed edges of a bolt. Its defining characteristic is its enclosed, domed upper portion, which safeguards the thread from harm while providing the entire fitting with a clean, polished look.

Cap nuts feature a straightforward yet practical design. The curved dome serves dual purposes - it shields the threads from rust and oxidation while eliminating the risk of injuries from exposed sharp threads.

One essential purpose of a cap nut is to safeguard the visible threads of a bolt or screw. Through thread coverage, cap nuts prevent the entry of debris, water, and other damaging substances. This protection stops deterioration that might compromise the connection and lead to fastener failure eventually.

Basic cap nuts display a basic dome configuration, functioning to shield the bolt or screw end. These represent the most widely used variety, engineered to preserve threads while delivering a refined appearance. They typically serve in common applications requiring both thread protection and visual appeal.

Sometimes referred to as domed cap nuts, acorn nuts showcase a rounded peak resembling an acorn shape. These components are primarily chosen for decorative purposes where an elegant, refined look is desired. Found in both regular and tall crown versions, the latter suits longer studs by providing enhanced protection.

Push Nuts, constructed from materials such as aluminum, enable quick installation. These components can be directly pressed onto the bolt or stud without requiring tools. They're frequently used where rapid assembly is needed or when using decorative finishes.