Screws DIN 603, ISO 8677 and UNI 5731 are fasteners used for both wood and iron. These screws, also known as round-head screws with an under-head square, are characterised by having a square immediately below the round head with an anti-unscrewing function when inserted into a square hole. The round shape of the head, with little protrusion and no indentation or edge, makes this type of screw particularly suitable in an anti-unscrewing function. These screws are used in a wide range of applications, including door and window frames, furniture construction, gates, sheet metal products, street furniture, benches, fences, gates, guard rails. DIN 603, ISO 8677 and UNI 5731 screws can be made of various materials, including stainless steel, carbon steel and special alloys. In addition, they are available with a variety of surface treatments to improve corrosion resistance, such as galvanising.