These Forgefix Carriage Bolts are Zinc Plated, and ideal for timber to timber joining. They come complete with a hex nut and are fully threaded to 100mm. Also known as 'Cup Square Hex Bolts', the square underneath the Cup stops rotation of the bolt when tightening. Conform to DIN 603 and DIN 934 standards. Available in a comprehensive range of sizes to suit most applications. APPLICATIONUsed mainly for fastening timber to timber and is extensively used for timber joist construction in house building and numerous decking applications. A Carriage Bolt, also known as a Coach Bolt or as a ‘Fully Threaded Cup Square Hex Bolt’, has a domed or countersunk head, and the shank is topped by a short square section under the head. The square section grips into the part being fixed (typically wood), preventing the bolt from turning when the nut is tightened. A rib neck Carriage Bolt has several longitudinal ribs instead of the square section, to grip into a metal part being fixed. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrate’s surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers. Ref: UTTK13941