What kind of marking denotes a 'D' type rivet?

A 'D' type rivet is specifically identified by a raised dot marking on its head. This marking system is used in aviation to distinguish between different types of rivets, which helps in ensuring the correct rivet is used in specific applications. The raised dot provides a quick and efficient visual cue for technicians during inspections or when selecting rivets for a job.

The other markings mentioned, such as cross, dimple, and double dash, do not correspond to 'D' type rivets. Each has its own unique designation, aiding in the differentiation of rivet types and ensuring proper application in aircraft construction and repair. Thus, the raised dot marking serves as a definitive identifier for 'D' type rivets, streamlining the process for those working with aircraft components.