What is the most common type of washer used in fastening systems?

The flat washer is the most common type of washer used in fastening systems due to its fundamental role in distributing the load of a threaded fastener such as a bolt or nut. By providing a smooth, flat surface for the fastener to bear against, flat washers help prevent damage to the material being fastened and reduce the risk of the fastener loosening over time. They are widely utilized in various applications across construction and mechanical assemblies, making them a staple in any toolbox.

Flat washers are also versatile and can accommodate a range of sizes and types of fasteners, allowing for easy integration into different projects. Their simplicity and effectiveness make them the preferred choice compared to other washer types, which serve more specialized functions. For instance, lock washers and spring washers are designed to prevent loosening under vibration or movement, but they are not as universally applicable as flat washers. Similarly, fender washers are used mainly for larger holes or to distribute loads over a wider area, which limits their use in comparison to flat washers.