This carriage bolt series stands out for its high strength and versatile sizing, crafted to meet Grade 8.8 performance standards—meaning it boasts a minimum tensile strength of 800MPa and yield strength of 640MPa, delivering reliable load-bearing capacity for medium to heavy-duty fastening needs. The bolt features a distinctive design: a smooth, rounded head with a square neck beneath it. This square neck prevents the bolt from spinning when tightening the nut, eliminating the need for a second tool to hold the bolt, which streamlines installation even in tight spaces.

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.