Short selling refers to selling standard contracts at prices that are expected to fall in the future, and buying them after the market falls to make a profit. Futures implement a margin mechanism, trading the standard contract of the commodity rather than the commodity itself. Therefore, only a certain margin is needed in futures, and goods can be bought and sold directly as needed. Short selling is the operation of selling commodity contracts directly when the expected commodity prices fall. Because we are selling commodity contracts for delivery at a specific time in the future, we only need to fulfill the contracts before the expiration date, and there is no need to have corresponding contracts when selling. Means of performance are divided into hedging and delivery. Hedging refers to buying equal contracts to close positions, and delivery refers to taking out qualified physical objects.