What does the Rule of 18 refer to in high line operations?

The Rule of 18 in high line operations is primarily concerned with ensuring the safety and integrity of the system under tension. This rule provides guidelines on the maximum force that can be safely applied when tensioning a high line, typically recommending that the total tension should not exceed 18 times the weight of the load being lifted or moved. This guideline helps to prevent potential failure of the rope or rigging systems by establishing a safe operational threshold, thereby reducing the risk of accidents during high line rescue operations.

In contrast to this understanding, the other options address different considerations. While crowd control is an important aspect of rescue operations, it is not related to tensioning in high line setups. Similarly, setting limits on the number of rescues or specifying angling for high lines does not align with the core principle of managing tension forces, which is what the Rule of 18 specifically addresses.