What kind of marking denotes an 'AD' type rivet?

An 'AD' type rivet is identified by its characteristic dimple marking. This marking indicates the specific design and strength characteristics of the rivet, which is made from aluminum alloy and features a dome-shaped head. The dimple signifies that it is a tight tolerance rivet, ensuring a secure fit when employed in aircraft structures. The designation of 'AD' distinguishes it from other types of rivets, which may not have this distinct marking or may be designed for different purposes or materials.

Understanding the markings on rivets is crucial for ensuring the correct selection and application in aircraft maintenance and repair, as using the wrong type of rivet can lead to structural failures.

In contrast, options such as a cross or plain marking do not represent a unique identifier for 'AD' rivets, while a double dash does not relate to any standard marking for any type of aircraft rivet.