When using a chain puller, the jaws are opened and closed by __________.

The operation of a chain puller typically involves a mechanism that allows the user to open and close the jaws to grip the chain effectively. The correct answer indicates that this action is controlled by a dial located on the top of the tool. This design allows for precise adjustments and ensures that the jaws can be opened or closed smoothly and securely, providing an effective grip on the chain when pulling or lifting loads.

Using a dial is advantageous because it allows for controlled and incremental adjustments, minimizing the risk of over-tightening or damaging the chain. It also provides a more ergonomic way to operate the tool, as the user can maintain control while focusing on the task at hand.

In contrast, operating the jaws by hand may not provide the same level of precision and can lead to uneven gripping. Using a jaw inserted into the chain is not a typical method for operating a puller as the jaws should engage the chain directly, rather than relying on another component for engagement. A torque wrench is designed to apply a specific amount of torque and does not operate the jaws of a chain puller, making it irrelevant in this context.