What mechanism prevents overextension of the fly section of an extension ladder?

The correct choice, stops, refers to the components of an extension ladder designed specifically to prevent the fly section from being overextended. These stops are usually located at the junction where the fly section connects to the bed section of the ladder. They ensure that there is a maximum limit to how far the fly section can be extended, which is critical for maintaining the ladder's stability and safety during use.

When firefighters extend an extension ladder, having stops in place is vital as it helps prevent the fly section from being pulled too far out, which could lead to instability or potential failure of the ladder under weight or adverse conditions. This safety feature is an integral part of ladder design, ensuring that operators can work effectively while minimizing the risks associated with ladder use in emergency situations.

Other mechanisms such as guides or locks may assist in the operation and positioning of the ladder but do not serve the primary function of preventing overextension as effectively as stops do. Depending on their design, pawls might engage to lock sections of the ladder in place but again, do not specifically limit the extension distance like stops do.