Compliant with ASME B18.5 and SAE J429 standards, this Grade 8 carriage bolt is crafted from premium medium-carbon alloy steel, quenched and tempered to deliver exceptional mechanical performance—boasting a minimum tensile strength of 1040MPa and yield strength of 895MPa . Its signature design features a smooth domed head and integral squared neck, which locks into pre-drilled holes to prevent rotation during installation, enabling secure tightening from the nut side without extra tools . The fully threaded shank ensures maximum grip and uniform load distribution, making it ideal for thick materials and high-stress assemblies.

It is distinguished from other bolts by its shallow mushroom head and the fact that the cross-section of the shank, though circular for most of its length (as in other kinds of bolt), is square immediately beneath the head. This makes the bolt self-locking when it is placed through a square hole in a metal strap. This allows the fastener to be installed with only one wrench, working from the opposite end. The head of a carriage bolt is usually a shallow dome. The shank has no threads and its diameter equals the size of the square cross-section.

The carriage bolt was devised for use through an iron strengthening plate on either side of a wooden beam, the squared part of the bolt fitting into a square hole in the ironwork. It is common to use a carriage bolt on bare timber, the square section giving enough grip to prevent rotation.

The carriage bolt is used extensively in security applications, such as locks and hinges, where the bolt must be removable from one side only. The smooth, domed head and square nut below prevent the carriage bolt from being gripped and rotated from the insecure side.