More, kill more:

It is generally believed that the stock price will rise that day, so there are many people grabbing long hats in the market. However, the stock price does not rise significantly. When the transaction is about to end, There is a rush to sell, resulting in a sharp drop in the closing price.

To put it simply, the practice of buying stocks and then selling them immediately is called long-killing.

Short killing:

It is generally believed that the stock price will fall that day, so everyone rushes to short the hat. However, the stock price does not fall significantly, so they cannot buy at a low price. Before delivery, they have to cover their positions. This situation causes the stock price to rise significantly at the closing time. As opposed to killing more and killing more.

Limitations on client positions.

In order to prevent large investors from holding excessive positions and manipulating the market, most exchanges implement coding management for customers represented by member units. Each customer can only use one transaction code. The total amount of positions is also limited. For example, for soybean futures contracts on the Dalian Commodity Exchange, the net position (the difference between long positions and short positions) of each customer code in a general contract month shall not exceed 2,000 lots, starting from the first trading day of the month before the delivery month. 600 lots, 400 lots starting from the tenth trading day of the month before the delivery month, and 200 lots in the delivery month. During the implementation of the position limit system, if a member or customer has pending positions on multiple seats at the same time, Their positions must be consolidated and calculated. The large-capacity reporting system is another system closely related to the position limit system to control trading risks and prevent large-scale traders from manipulating the mid-term behavior. When the amount specified by the exchange is exceeded, it must be reported to the exchange. The content of the declaration includes the customer's account opening status, transaction status, trading motivation, etc., so that the exchange can review whether large investors have excessive speculation and market manipulation, as well as the behavior of large investors. Trading risk conditions. For example, the Shanghai Commodity Exchange’s large account reporting system stipulates that when a trader’s position reaches 80% of the exchange’s position limit, members or customers should report their trading positions and funds to the exchange. For members or customers suspected of market manipulation, the exchange must restrict them from establishing new positions or require them to close their positions at any time until the exchange implements forced liquidation.