A flag can be used as an entry pattern for the continuation of an established trend. The formation usually occurs after a strong trending move that can contain gaps (this move is known as the mast or pole of the flag) where the flag represents a relatively short period of indecision. The pattern usually forms at the midpoint of a full swing and consolidates the prior move. Price is contained by 2 parallel trend lines that lie close together and are sloped against the mast.
Bullish flags can form after an uptrend, bearish flags can form after a downtrend. The pattern has completed when price breaks out of the containing trend lines in the direction of the prevailing trend, at which point it will likely continue its course. Conservative traders may look for additional confirmation of the trend continuing. The target can be estimated through the technique of measuring the length of the mast and extending it in the direction of the breakout. A common stop level is just outside the flag on the opposite side of the breakout.