We showed you earlier in the chapter how a histogram could be constructed that plots the difference between two moving average lines. Using that same technique, the two MACD lines can be turned into an MACD histogram. The histogram consists of verti­cal bars that show the difference between the two MACD lines. The histogram has a zero line of its own. When the MACD lines are in positive alignment (faster line over the slower), the his­togram is above its zero line. Crossings by the histogram above and below its zero line coincide with actual MACD crossover buy and sell signals.The real value of the histogram is spotting when the spread between the two lines is widening or narrowing. When the histogram is over its zero line (positive) but starts to fall toward the zero line, the uptrend is weakening. Conversely, when the histogram is below its zero line (negative) and starts to move upward toward the zero line, the downtrend is losing its momentum. Although no actual buy or sell signal is given until the histogram crosses its zero line, the histogram turns provide earlier warnings that the current trend is losing momentum. Turns in the histogram back toward the zero line always precede the actual crossover signals. Histogram turns are best used for spotting early exit signals from existing positions. It's much more dangerous to use the histogram turns as an excuse to initiate new positions against the prevailing trend.