Which statement about the triangle on the bolt head is correct?

• A. It marks a high-strength bolt.
• B. It marks a close tolerance bolt.
• C. It indicates a metric bolt.
• D. It indicates corrosion resistance.

Answer: (B)

The triangle on the bolt head identifies a close-tolerance bolt. These bolts are manufactured to tighter dimensional limits than standard bolts, giving a more precise fit in the joint and reducing looseness or misalignment under load. That precise fit is important in critical assemblies where accurate alignment and even load transfer matter, so the triangle serves as a quick visual cue to use the correct hardware in those locations. This mark does not indicate high strength by itself—strength is shown by other markings or the grade designation—nor does it indicate metric sizing or corrosion resistance, which depend on different indications such as metric numbers or material/coating details. Use is guided by the maintenance instructions or drawings that specify close-tolerance bolts for specific joints.