A double bottom is a bullish reversal pattern that usually occurs after an extended downward movement in price. In good double bottom patterns, the second trough is typically lower than the first trough.
Trading the pattern: The confirmation level in a double bottom is the price at the peak of the two troughs. Draw a horizontal price line through that price level and if price closes above that level, it is a signal for a bullish entry.
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 distance 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 A can be expected.