A ________ is used to hold the ball joint to the steering knuckle.

The correct answer is the pinch bolt, which is specifically designed to hold the ball joint securely to the steering knuckle. In this type of assembly, the pinch bolt creates a clamping action that captures the ball joint and prevents it from moving independently of the steering knuckle, ensuring stable steering and suspension performance. This connection is crucial for maintaining vehicle control and preventing excessive wear or potential failure of the steering components.

Rivets and kingpins serve different purposes in automotive applications; rivets do not provide the adjustable, removable connection needed for servicing components like ball joints, while kingpins are associated with older steering systems and primarily function as pivots for steering. Similarly, strut rods are typically part of a suspension system and serve a different role in controlling axle motion, rather than securing a ball joint.