What tool is commonly used to observe the wear indicator on ball joints?

The correct tool for observing the wear indicator on ball joints is a pry bar. This tool is specifically designed to apply leverage, which allows a technician to pivot or lift the control arm. When the control arm is manipulated, the technician can closely inspect the ball joint for any signs of wear, including movement or abnormal play. The wear indicator is typically a small mark or visual indicator that helps assess the condition of the ball joint; thus, using the pry bar facilitates a thorough examination during servicing.

Other tools mentioned, such as a torque wrench, are used to measure and apply specific torque settings when tightening fasteners, but they do not assist in examining the physical condition of ball joints. A frame machine is primarily used for aligning the chassis of the vehicle after a collision, and it does not provide insight into ball joint wear. Lastly, a hydraulic lift is utilized to raise the vehicle, giving access for inspection and repair, but it does not directly help in observing the wear indicator specifically on ball joints. Therefore, a pry bar remains the best choice for this task.