A safety washer, also known as a lock washer or a split washer, is a type of washer that is designed to help prevent loosening due to vibration or torque. It is typically made of a flexible material, such as spring steel or plastic, and has a split or notched design that allows it to compress slightly when tightened down. This creates a spring-like action that helps to maintain a constant pressure on the fastener and the material being fastened, helping to prevent loosening. Safety washers are often used in applications where a secure hold is necessary, such as in the assembly of engines, gearboxes, and other mechanical components. They can also be used in electrical and electronic applications to help prevent the loosening of terminal connections.