A Bull Flag is a bullish continuation pattern that generally occurs after a large run up in price. After a period of price consolidation in the flag, prices generally continue in the direction of the prior trend.
A Bull Flag can be identified a long green candlestick that resembles a flagpole, and a flag which resembles a rectangle marked by two parallel lines that slope against the prevailing trend.
Measuring the move: Add the vertical distance of the flagpole to the breakout and this would give you an approximate price target for the next run up in price.
Trading the pattern: Traders should be watching the upper trend line of the pattern. A bullish entry signal is when price pierces through the upper trend line.