Running Flat
A running flat is one of the rarest corrective patterns you will encounter. The structure is A-B-C (3-3-5) like other flats, but with a twist. Wave B exceeds the start of Wave A, just like in an expanded flat. The difference is that Wave C fails to reach the end of Wave A. It falls short. This tells you the larger trend is extremely strong. The correction cannot even make a meaningful pullback because buying or selling pressure in the trend direction is overwhelming. Running flats are hard to identify in real time because they look incomplete. You keep waiting for Wave C to finish its decline, but it just reverses early. When you spot one in hindsight, it confirms powerful trend momentum. They appear most often in Wave 2 of a third wave extension.
EUR/USD is in a strong uptrend. Wave A drops from 1.1200 to 1.1100. Wave B rallies past the start of A to 1.1250. You expect Wave C to drop below 1.1100, but it only reaches 1.1120 before reversing sharply higher. Wave C fell short of Wave A's endpoint. The running flat signals intense bullish pressure. The next impulse wave up is likely to be explosive. A trader who recognizes this pattern enters long at 1.1120 with a stop below 1.1050.