M20 Carriage Bolts a large threaded bolt with a dome head of which is a fixed a square under the head the same size as the diameter of the shank. The square stops the bolt from turning when you tighten the nut on the end of the threaded portion. This produces an attractive finish one end without the risk of catching clothing and hands due to the domed head.
Coach Bolts are available in Zinc, Galvanised and Stainless Steel.
An ideal solution for playgrounds, garden furniture, arbors, gazebos, car ports etc.
Anothe name for Coach bolts is Cup Square Hex cup being the head square under the head and hex the nut. Carriage bolts is another name often used referring to old railway carriages etc.