Charting software also allows the drawing of Gann and Fibonacci fan lines. Fibonacci fan lines are drawn in the same fashion as the speedline. Except that Fibonacci lines are drawn at 38% and 62% angles. (We'll explain where those 38% and 62% numbers come from in Chapter 13, "Elliott Wave Theory.") Gann lines (named after the legendary commodity trader, W.D. Gann) are trendlines drawn from prominent tops or bottoms at specific geometric angles. The most important Gann line is drawn at a 45 degree angle from a peak or trough. Steeper Gann lines can be drawn during an uptrend at 633/4 degree and 75 degree angles. Flatter Gann lines can be drawn at 261/4 and 15 degree lines. It's possible to draw as many as nine different Gann lines.
Gann and Fibonacci lines are used in the same way as speedlines. They are supposed to provide support during down­ward corrections. When one line is broken, prices will usually fall to the next lower line. Gann lines are somewhat controversial. Even if one of them works, you can't be sure in advance which one it will be. Some chartists question the validity of drawing geo­metric trendlines at all.