This is to allow any moisture from the cargo or sweat from the bulkheads to run across to the limber holes in the wings and so down to the bilges.
Le nto kukuvumela ukufuma okusuka kumthwalo okanye embilweni osuka kwicandelo lenqanawa elingangeni manzi okokuba zibalekele ngaphesheya komngxuma wenqwelo yenkanunu emaphikweni kunye nokuya phantsi kumphantsi wenqanawa.