While working from a ground ladder, the hook on the safety harness should be:

When working from a ground ladder, it is essential for safety that the hook on the safety harness is attached to a rung of the ladder. This practice ensures that the firefighter maintains a secure connection to the ladder, reducing the risk of falling and providing stability while conducting operations.

By attaching the safety harness to a rung, firefighters can securely position themselves on the ladder while keeping their hands free to operate tools or execute other necessary tasks. This method is particularly important for maintaining balance and enhancing the effectiveness of the firefighter’s efforts during firefighting or rescue operations.

The other options do not provide the same level of security or safety. For example, attaching the hook to a tool may lead to an unbalanced situation or the potential for the tool to become dislodged, while looping the hook around the ladder does not create a secure and reliable attachment. Tying it to the firefighter's belt could restrict movement and does not offer the same safety benefits as securing it to a rung. Hence, attaching the safety harness hook to a rung is the best and safest practice when working from a ground ladder.