Space holder for a blue, white and green space

If we take, for example, a scenario of queueing somewhere, say, in a supermarket, when we realise we have forgotten something we need to fetch; it is not uncommon to turn to the person behind to ask if they wouldn’t mind saving our space. By saving our space, we are asking them to hold it for our return.
In this simple act, a stranger undertakes a social contract when they vow to keep our claim on a space. Another’s recognition bounds the held space, creates a territorial limit albeit invisible to others milling about close-by.
The space is concrete through a stranger’s validation. It is intersubjective through an arrangement between two people. And is actual as a social space in public, not a figment of one’s imagination.