Combination screws refer to a combination of a screw with a spring washer and a flat washer, which are fastened together by rolling the threads. 2. The role of combination screws Combination screws with high-strength large hexagonal head bolts for steel structures are mainly used in railway and highway bridges, boiler steel structures, industrial plants, high-rise civil buildings, tower mast structures, lifting machinery and their steel structures where friction-type high-strength bolt combination screws are required. The role of combination screws is also very simple, which is to connect and fasten product objects. Because the spring flat washer is rolled on the screw, there is no need to equip it with a spring flat washer when using it. And when in use, the combination screw has another particularly important role, which is the anti-loosening effect. 3. Advantages of combination screws. The advantage of combination screws is that in terms of use, it saves the time of manual spring flat washers, and also improves the efficiency of screwing for some manufacturers such as electronic appliances that use a lot of screws. Some manufacturers that use a lot of screws need to use spring flat washers on some products when screwing. They have to use spring flat washers one by one. This is very time-consuming, labor-intensive, and expensive. 1. Pre-assembled components ensure faster assembly speed. 2. Reduce failures caused by human error, improper assembly or forgetting to install lock washers. 3. Facilitate assembly of extremely small products. 4. Allow maintenance and repair in hard-to-reach or restricted areas. 5. Reduce item numbers, optimize inventory and logistics, and save costs. 6. Disassembly is faster and easier, as loose lock washers are difficult to remove, especially from countersunk holes.