What is the purpose of a tag line during hoisting operations?

The purpose of a tag line during hoisting operations is to control the load and prevent rotation. When a load is lifted, it can swing or rotate due to wind or uneven lifting. By using a tag line, operators on the ground can manipulate the load gently from a safe distance, helping to stabilize it and ensure it moves smoothly to its intended position without unexpected movements. This added control contributes to the safety of the operation, minimizing the risk of accidents and damage to both the load and surrounding personnel.

In the context of the other options, marking the load's weight doesn’t apply, as tag lines are not designed for that function. Signaling workers at ground level typically involves communication tools or methods rather than a tag line. Measuring distances is also unrelated, as tag lines are specifically used for load stabilization rather than distance measurement. Thus, controlling the load and preventing rotation through the use of a tag line is crucial for safe hoisting operations.