Which feature of a lock washer contributes to preventing loosening?

The shape of the lock washer is crucial in preventing loosening because it is specifically designed to create a frictional grip between the bolt or screw and the material it is securing. Lock washers typically have a split or wave design that allows them to exert pressure against the fastener and the surface, which helps maintain tension and resist vibrations that might otherwise cause loosening over time. This shape facilitates a mechanical locking effect, making it more difficult for the fastener to back out, especially under dynamic conditions such as machinery operation or movement.

While other factors, such as the material, denting features, and size can have an impact on a washer's performance, the primary function that directly relates to loosening prevention is the unique shape designed to enhance friction and connection stability.