The gap between a powerful, wealthy family and common people is vast; used to express that once someone enters a high-ranking household, they are as inaccessible as if they were across the ocean.

once entering the gates of a noble family, one is as unreachable as if in the depths of the ocean; used to describe the difficulty of meeting someone once they have joined the elite or high society

Used to describe a high official's residence or a powerful family's house as being so heavily guarded and strictly controlled that common people cannot enter; also used to describe former lovers or friends being separated by social status and unable to meet.

to drag one's hem at the gates of the nobility, referring to the practice of seeking patronage or serving as an attendant to the powerful