What type of washer is typically a flat metal ring with no additional features?

The type of washer described as a flat metal ring with no additional features is indeed a flat washer. Flat washers are designed primarily to distribute the load of a threaded fastener, such as a screw or a bolt, over a larger surface area. This helps to prevent damage to the material being fastened and also prevents the fastener from loosening.

The absence of any additional features distinguishes flat washers from other types. For example, lock washers are specifically designed to prevent fastening devices from loosening due to vibration, whereas spring washers utilize elasticity to apply a constant force. Fender washers, on the other hand, have a larger outer diameter and are used to increase the bearing surface under the head of a bolt or nut, which is not a characteristic of plain flat washers. Understanding these distinctions clarifies why a flat washer is solely characterized by its simple, flat shape without any modifications or parts, making it essential in various fastening applications.