A bolt with a single raised dash on the head indicates what type of classification?

A bolt marked with a single raised dash on its head specifically indicates that it is an AN (Army-Navy) corrosion-resistant steel bolt. This marking system is used to provide quick identification of the bolt's material and its intended use, making it easier to select the right type of fastener for tasks where resistance to corrosion is crucial.

The significance of the single dash is rooted in military specifications, which categorize fasteners systematically. Corrosion-resistant bolts are typically made from materials that can withstand harsher environmental conditions, thereby ensuring durability and longevity in applications, especially where exposure to moisture or corrosive environments is anticipated.

While the other classifications listed have their own distinct marking systems, they do not coincide with the single raised dash characteristic that identifies corrosion-resistant steel bolts. Understanding these designations is critical for anyone involved in materials selection and processing in engineering or manufacturing scenarios.