Which marking indicates a plain rivet?

The marking that indicates a plain rivet is denoted by the letter "A." Plain rivets are commonly used in various aviation applications and are designed with a simple, unformed head. This type of rivet does not have any additional features for enhancing strength or grip, making it very suitable for general fastening purposes in aircraft structures.

When selecting the appropriate rivet for an application, understanding these markings is crucial. The "A" designation signals that the rivet is a standard, plain type, which is an essential choice for certain structural applications where minimal deformation is required during installation. This knowledge helps ensure that mechanical fasteners are selected and utilized correctly, which is vital for maintaining the integrity and safety of aircraft structures.