This saying indicated that in ancient times, professions could be divided out into at least 360 different ones. The number had grown in recent times.
There were also 360 professions in the US. Li Du's storage auction, old goods trading, and gem hunting were among the more niche professions.
He liked to refer to his main business of storage auction as "junk hunting." In fact, this was just a self-deprecating term; there were junk hunting professions in the US.
Dumpster diving was one such profession—an extremely niche profession.
The United States was the highest trash-producing country in the world. Dumpster diving was a popular profession; the homeless folks everywhere and the poor from the slums engaged in this profession.
Dumpster diving masters originated from these people. As the name suggested, they were masters of dumpster diving, and there were many such people in big American cities.