When are vertical side gaskets considered watertight?

Vertical side gaskets are deemed watertight when light does not leak through when the doors are locked. This indicates that the gaskets are effectively providing a seal that prevents water intrusion, which is critical for maintaining the integrity of the container. A watertight seal is essential for protecting the cargo from moisture and ensuring that the container is suitable for transporting goods under conditions that may expose it to water, such as rain or being submerged in water.

This assessment focuses on the practical performance of the gaskets in real-world conditions—if no light escapes, it suggests that the gaskets are properly seated and functioning as intended. While new gaskets (often mentioned in other options) typically do provide a better seal, the assessment of watertightness hinges on actual performance rather than the physical state or appearance of the gaskets.