A sharp rally (the pole) followed by a short, tight, flat or downward-sloping channel; completes on a close above the flag's upper line.
Flags are brief pauses after a fast move. Edwards & Magee say they "fly at half-mast": the move after the break often resembles the pole.
Flags are short by nature, so the usual 2-month minimum length does not apply.
How we define it
Pole: a run of at least 5 ATR and 8% (4H) / 15% (1D) / 25% (1W) in 3-30 candles (4H), 3-20 (1D) or 2-8 (1W), at least 0.6 ATR per candle, no single candle making up half of it
Flag: 6-36 candles on 4H, 5-25 on 1D, 3-8 on 1W, and no longer than twice the pole
Two parallel lines with at least 2 touches each, flat or sloping against the pole; no close outside them; the flag gives back at most half of the pole and is no taller than half of it
Breakout (up) / breakdown (down): the first candle close beyond the boundary by at least 3% on 1D and 1W (1.5% on 4H)
Failed breaks: a breakout or breakdown that closes back inside the boundary within 6 candles on 4H, 5 on 1D or 3 on 1W is removed from the list
Trend filter: breakouts only above the 200-period EMA (40-week EMA on 1W), breakdowns only below it
Watchlist: the pattern is complete but unbroken and price is within 3% (or 1 ATR, at most 6%) of the boundary