The main function of decision lines is to indicate the mid-term reversal trend of prices and guide the operation of price bands within the established trend. When the price breaks the decision line upwards or downwards in volume, it indicates that a large-scale reversal market has started, and corresponding trading decisions should be made in the near future. When the price breaks through the decision line, it generally does not move in the opposite direction in a short period of time, that is, the main force makes a bullish or bearish move, at least it will run above or below the decision line10~25It takes about one trading day to reverse.