What should a firefighter check to ensure is locked before climbing an extension ladder?

Before climbing an extension ladder, a firefighter should check that the dogs are locked. The "dogs" are the locking mechanisms that secure the extension sections of the ladder in place. When the dogs are properly engaged, they ensure that the sections of the ladder remain stable and fixed in their extended position, which is critical for the safety of the firefighter while ascending or descending.

If the dogs are not locked, there is a risk that the ladder could collapse or slide back down, leading to potential falls or injuries. The stability that the dogs provide allows firefighters to perform their tasks safely, knowing that the ladder will support their weight and not inadvertently retract or collapse while in use.