What is the primary purpose of a Jack Line?

The primary purpose of a Jack Line is to connect safety harnesses to the rigging. This specialized line is critical in ensuring the safety of personnel working at height, allowing them to secure themselves when working on or near areas where there is a risk of falling. Jack Lines help to prevent accidents by providing a reliable means to tether the worker, ensuring that they remain safe while performing their tasks.

The other options relate to different aspects of rigging, but do not accurately describe the function of a Jack Line. For example, measuring the height of rigged equipment is more typically done with tools designed for that purpose rather than a line. While heavy hemp line systems may require pulling, this is not the primary function of a Jack Line, which is specifically about safety when working at heights. Similarly, although supporting flying scenery is a crucial part of theatrical rigging, it is separate from the safety connection that a Jack Line provides.