What does rear sill downward deformation need to ensure regarding lower surfaces?

The correct answer highlights that the rear sill downward deformation must not surpass the lower surfaces of the corner fittings, which is critical for maintaining the structural integrity and overall utility of the dry van. The corner fittings play a vital role in securing the container to its base and ensuring that it remains stable during transport. If the deformation exceeds these lower surfaces, it could compromise secure attachment and alignment, leading to potential safety hazards and operational inefficiencies.

In addition, this standard ensures that the container maintains its intended design specifications, which aids in avoiding misalignment issues that could arise during stacking or securing of the container. Maintaining the proper relationship between the rear sill and the corner fittings is essential for compatibility with different handling equipment and for meeting industry standards.