The way to make money by buying down is actually very simple. For example, investors expect the market to fall, borrow spot crude oil when the price of spot crude oil is high, buy it when the oil price falls to a certain level, and return it to the exchange at the current price. This mode of shorting spot crude oil can make a profit in the band where the price falls, and the difference is the profit. This is called emptiness, which is just the opposite of doing more.
Empty orders are the direction that investors think crude oil prices may fall in the future, and then place orders to buy and fall. This contract is called an empty order, and the technical term is also called "short selling". Suppose an investor places an empty order when the crude oil price is $65438 +02. If the price of crude oil drops to $8 in the later period and investors close their positions, the order will make a profit, and the profit amount is $65,438 +02-8 = 4.