Look at the buying signal of the bollinger band: when the channel trend of the bollinger band is upward, the opening of the bollinger band is gradually narrowed, and when the numerical difference between the upper and lower rails is close to 10%, the trading volume is obviously enlarged, and the futures price is broken, so you can buy.

Look at the selling signal of bollinger band: when the trend of bollinger band is upward, the opening of bollinger band changes from narrow to wide, and the futures price goes up, so it can be sold on rallies.

BOLL, also known as Bollinger Band, uses statistical principles to find out the standard deviation and confidence interval of futures prices, thus determining the fluctuation range and future trend of futures prices, and using bands to display the safe high and low prices of futures prices.