There are many terms for futures. When observing the futures market, we often see the concepts of double opening, double flat, multi-opening, empty opening, multi-flat, empty flat and changing hands in the dynamic position change table. The meaning is as follows: double opening: at the same price, long and short positions are opened at the same time, and the total position is increased by double flat; At the same price, long and short positions are closed at the same time, and short positions reduce the total position: investors without positions open positions. And sell more open positions: investors who have no positions judge the market to rise, but buy short positions: investors who have sold open positions buy and close positions; Investors who have bought and opened positions, sold and closed positions; Investors who hold multiple orders, sell and close positions, new investors buy and open positions, and short positions are traded at the same price; Investors who have held empty orders buy positions and leave.