A double top is a bearish reversal pattern that typically occurs after an extended upward movement in price. Prices reverse once, moving downwards to the confirmation level followed by an upward movement in price. Prices reverse again at the second peak, and completion of the pattern occurs when prices break through the confirmation line.
Measuring the move: Measure the distance between the price at the peak of the pattern and the price at the lowest low of the pattern. This difference is then added to the confirmation line after the break out, what this means is that an upward price movement from the breakout point plus the height of the pattern can be expected.
Trading the pattern: The confirmation level in a double top is the price at the bottom of the two peaks. Draw a horizontal price line through that price level and if price closes under that level, it is a signal for bearish entry.