Gold sits quietly near 2380 for six hours, then in three candles jumps to 2410 and never looks back for the rest of the day. That launch point, the small range price left behind violently, is a supply or demand zone: a footprint of the moment a large order overwhelmed the resting liquidity at that price and the market simply could not stay there. Traders who mark these zones are not drawing decoration. They are marking the addresses where big size already showed up once.
What actually makes a zone
A zone is not a random consolidation. Look for a tight base, several small candles trading in a narrow band, followed by a departure candle that is unusually large relative to the recent average and closes near its extreme with almost no opposing wick. On EURUSD, a 15 pip base held for two hours followed by a 40 pip breakout candle marks a demand zone at the base if the move was up, or a supply zone if down. The base is the zone, not the launch candle, and it should be drawn as a range of a few pips or points wide, not a single line, since price rarely returns to the exact tick.
Fresh zones behave differently from tested ones
A zone price has never revisited is fresh, and fresh zones tend to react more strongly, because the original imbalance between buyers and sellers there has not yet been resolved by anyone getting a second chance to trade it. Each time price returns to a zone and reacts, some of that original imbalance gets filled, and the zone weakens. A demand zone on the Nasdaq that has already produced two clean bounces is a different, lower-probability trade the third time price arrives, even though the lines on the chart have not moved. Tracking how many times a zone has been tested matters as much as marking the zone in the first place.
Trading the return
The setup is straightforward: mark the zone, wait for price to return to it, and look for a rejection candle inside the zone before entering, rather than buying or selling the instant price touches the line. On a $10,000 account, a EURUSD demand zone 10 pips wide with a stop 5 pips below its base sizes to roughly $100 of risk at 2 lots on a tight stop, or scale the stop wider if the zone itself is wider. The target is the next opposing zone or an obvious structural level, and the trade is only taken if the approach into the zone looks like a genuine pullback, slowing candles with shrinking size, rather than a fast, aggressive drive that suggests the level will be run straight through.
When a zone simply fails
Zones fail, and treating them as guaranteed support or resistance is the same mistake as treating any level that way. A failure looks like price entering the zone and closing beyond its far edge with a strong body, rather than stalling and reversing inside it. On gold, price re-entering a 2380 to 2385 demand zone and closing at 2376 on a wide-range candle is a failure, and the correct response is to respect the new information and exit or flip bias, not to add to a losing position on the belief that the zone must eventually hold. Zones describe probability, not certainty, and every one of them eventually gets consumed.
A failed demand zone frequently becomes a supply zone afterward, the same way broken support often turns into resistance. The footprint that once marked aggressive buying now marks the price where the market decisively changed its mind, and traders who track that flip get a second useful level out of one original mistake instead of just erasing the line and moving on.