How do side and end panels contribute to the overall capacity of a dry van?

The correct answer underscores the critical role that side and end panels play in securing the load inside a dry van. These panels form the outer boundaries of the cargo area, helping to contain and stabilize the cargo during transport. Effective containment is essential for preventing movement of the load, which not only ensures the integrity of the cargo but also maximizes the use of space within the van. When cargo is secured properly against the side and end panels, it allows for safer transport and can prevent damage that might occur from shifting loads.

The other options describe various attributes that components of a dry van might have, but they do not directly pertain to the primary function of side and end panels in maximizing capacity. Insulation is more relevant for temperature control rather than capacity; structural support relates to the overall strength but not specifically to load containment; and ventilation is not a characteristic of dry vans, which are designed to protect cargo from external elements. Therefore, the containment of the load securely is the most accurate aspect regarding the contribution of side and end panels to the overall capacity of a dry van.