The call wall and the put wall: a ceiling and a conditional floor

The call wall

The call wall is the strike, above price, where the market makers' positive gamma is most concentrated. Mechanically, as price approaches it, long-gamma market makers sell ES into strength, and they sell more and more per point traveled.

Typical behavior: a ceiling that attracts then resists. Price is pulled toward it (market makers buy back their hedges on dips, charm helping), slows as it approaches, and struggles to get through without a massive outside flow. It is where an absorption in the order book has a good chance of holding: your order flow read and the hedging flow point the same way.

A call wall migrates slowly upward when the market rises (clients roll their call sales higher), and it is often the last to move: it marks the day's high more often than any technical level.