A hex nut is one of the most popular fasteners, the shape of a hexagon so has six-sides. Hex nuts are made from a number of materials, from steel, stainless steel to nylon. They can fasten a bolt or screw securely through a threaded hole, the threads tend to be right-handed. With six sides it makes it easier to work with, tools such as a spanner, or a ratchet make it very versatile to tighten or loosen. Nuts work through a combination of friction on the thread and compression of the parts together, but for sull thread engagement it must at least go through two full threads and must extend beyond the bolt. The finish of a bolt can vary also, from zinc plating to galvanizing offering corrosion resistance within harsh environments. If corrosion is an issue then a stainless steel nut is a better choice. It's advisable to match the materials of bolts/screws, washers and hex nuts, this will avoid any loose fittings.