Bolt Head Markings

The Bolt Head Markings guide from Allfast Solutions NZ helps you quickly identify the strength, grade, and origin of bolts used across construction and engineering projects. Each marking tells a story, and by learning what they mean, you can ensure every fastener you select is both safe and reliable.

Every bolt head includes specific markings that reveal its material grade and tensile strength. In other words, these small symbols carry important information about performance and compliance. With this guide, you’ll gain the confidence to recognise and interpret those markings — whether you’re inspecting hardware, ordering replacements, or checking installation standards.

Our Bolt Head Markings page includes:

• Common identification markings for metric and imperial bolts

• Grade systems explained (4.6, 8.8, 10.9, 12.9, and more)

• Visual comparisons for stainless steel and galvanised finishes

• Manufacturer symbols and how to trace product origins

• Quick-reference chart for on-site use

• Helpful advice on choosing the right bolt grade for your project

Moreover, each diagram is clearly labelled and easy to read, so you can identify differences at a glance. Using the correct bolt grade not only improves structural strength but also ensures compliance with New Zealand building and safety standards. Additionally, understanding bolt head markings reduces guesswork and promotes long-term reliability in your fastening work.

At Allfast Solutions NZ, we aim to support tradespeople and engineers with both quality products and trusted knowledge. Therefore, this resource goes beyond a simple chart — it’s a tool to help you work smarter, safer, and more efficiently.

For further reading, explore the International Organization for Standardization (ISO). This international standard outlines the technical requirements and testing methods that underpin the markings shown on most commercial bolts.

In summary, this Bolt Head Markings guide is perfect for on-site checks, quality control, and training. Keep it nearby whenever accuracy, safety, and professionalism matter most.