A fair value gap that fails — price closes all the way through it, and the level flips from support to resistance. Where the retest closes relative to the gap's 50% (CE) is often the tell.
Setup
Price drifts up normally, one candle at a time.
SETUPGAPVIOLATEINVERTREJECT
The inversion doesn't always look like this
Fully closed through — like above: one candle closes completely past the gap, flipping it from support to resistance.
The 50% (CE) is the tell — a close above it still favors the original direction; a close below it favors the flip. A wick alone proves nothing either way.
Works the other way too — a bearish FVG that gets closed through flips into support, the same idea mirrored.
Already inverted intrabar — on a lower timeframe, the flip can already be tested and confirmed before the higher-timeframe candle closes.