Securities companies' margin financing and securities lending business did not exist in China in the past, but it seems to exist now.

That is, when you think a stock will fall in the future, you can borrow a certain number of shares from a securities company by way of margin, such as the 30 yuan you borrowed. When a stock falls to a certain price and you know it will go up, you can buy the same number of shares in the stock market and return them to a securities company, such as 20 yuan. In this way, you earn 10 per share (but you need a certain handling fee, stamp duty, etc. However, if the price of this stock goes up, you will lose money. In the meantime, the securities company will make a deposit to urge you to pay.