Which of the following is NOT a method used for securing a firefighter to a ladder?

The method known as a chain harness is not typically used for securing a firefighter to a ladder. Firefighters implement specific techniques and tools to ensure safety and stability while working at height.

A leg lock, for instance, is a technique where a firefighter secures themselves to the ladder by using their legs to grip the rungs, allowing them to maintain a stable position. A ladder belt serves as a safety device, providing solid anchoring while enabling firefighters the necessary mobility to perform their tasks. The body wrap method involves securing the firefighter's body to the ladder for additional safety.

In contrast, a chain harness does not have a standard application within firefighting ladder operations. It's vital that the methods employed for securing firefighters are reliable, widely accepted, and facilitate effective work while minimizing risk. Therefore, the chain harness does not fit within this context, making it the correct answer.