How can you check the state of wear of the drawbar or the turntable of a full trailer?

Your answer is correct. To check the wear of the drawbar or turntable on a full trailer, you briefly pull forward with the towing vehicle while the trailer's parking brake is engaged. This creates a controlled stress on the connection, allowing you to detect any excessive play or looseness. Using the parking brake is essential because it holds the trailer in place while you apply force, ensuring an accurate check without the trailer moving forward. Other methods, like braking hard while driving or using the service brake, are unsafe or ineffective for this purpose.