Carriage bolts feature a round, domed head and square neck, which is specifically designed to fasten metal or wood to timber. Their square neck ensures stability by preventing the bolt from spinning once its been installed with a nut. We carry Grade 5 carriage bolts, which are made from quenched and tempered medium carbon steel, with a tensile strength of 120, 000 psa, that are also compliant with SAE J429 strength and hardness requirements and ASME B18.5 dimensional requirements