If you click on the chart above, you'll see how very significant volume entered the market in the ES 1109 area (red arrow), with the expanded volume occurring at both market bid and offer.
This is one of the first signs a market gives that a one-sided, directional market has finally attracted participation on the other side and is becoming two-sided.
That doesn't necessarily mean that the market move will reverse, but it does generally signify that buyers have found resistance at that price. Sharp short-term traders will use such market-generated information to help them figure out where to take profits on their positions, as the balanced demand and supply generally yields a period of consolidation.
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