Starships: Accommodations and Fuel Storage
V. If it's intended for additional fuel storage, access is by UNREP to the primary fuel tank, through the hull.
W. If it's for personnel or cargo, then either hatch(es), or airlock(s), through the hull.
X. We don't know if the external cargo mount is airtight, but we'll assume it isn't
Y. More important, if the side walls are solid, or just rails that corral the cargo.
Z. It's certainly implied that there are gates or hatches that allow access.