What type of rivet would have a 'Double Dash' marking?

The 'Double Dash' marking on a rivet indicates that it is a specific type known as a 'DD' rivet, which stands for "Double Dash." This marking is significant in the context of aircraft maintenance and assembly, as it helps in identifying the rivet material, design, and its intended use.

DD rivets are typically used in applications where specific strength and corrosion resistance are required, usually made from materials that offer good performance under various conditions. These rivets are often found in structural applications within the airframe where enhanced qualities are necessary, thus ensuring safety and reliability in aircraft construction.

The distinct marking system used for rivets serves to quickly communicate vital information to maintenance personnel, promoting effective identification without the need for extensive documentation. This efficiency is critical in aviation settings, where time and accuracy are paramount.