Which of the following is crucial when handling carabiners?

Loading a carabiner only along the axis of the spine is fundamental to ensuring its safe and effective use. The spine of the carabiner is designed to withstand the maximum load when loaded in this manner. This is because the spine is the strongest part of the carabiner, allowing it to bear the forces experienced during a rescue or climbing operation without risk of failure.

When a carabiner is loaded correctly along the spine, it maximizes its strength and integrity. Loads that deviate from this alignment—such as cross-loading or tri-axial loading—can significantly reduce the carabiner's strength, increasing the risk of failure during critical situations. Additionally, opening a loaded carabiner compromises its functionality and can lead to dangerous situations during rescue operations.

By adhering to the principle of loading a carabiner solely along the axis of the spine, rescuers can ensure the reliability and safety of their gear in high-stakes environments.