Call and put walls are strikes with concentrated dealer gamma. They act as gravity points for price — not because of technicals, but because of the mechanics of how market makers hedge.
A "wall" forms when options market makers hold a large net gamma position at a specific strike. The higher the open interest at that strike — particularly in near-term expiration options — the more hedging activity occurs as price approaches it. This hedging creates consistent, measurable buying or selling pressure that manifests as support or resistance in the underlying stock.
Unlike traditional technical analysis support/resistance (which is based on past price behavior), walls are forward-looking — they're defined by the current options positioning and will change as open interest changes.
A call wall forms at strikes where dealers hold large net long gamma from call options they've sold. As the underlying price rises toward this strike, dealers must sell increasing amounts of the underlying to remain delta-neutral. This selling pressure creates resistance.
The call wall is often described as a "ceiling." Price can and does break through call walls — but when it does, it typically requires sustained directional buying to overcome the dealer selling. A clean break above a major call wall is a meaningful signal.
A put wall forms at strikes where dealers hold large net short gamma from put options they've sold. As price falls toward this strike, dealers must buy increasing amounts of the underlying to maintain their hedge. This buying pressure creates support.
Put walls tend to be stickier than call walls — dealer buying flows are often absorbed by distressed sellers in declining markets, but the GEX-driven buying still tends to slow the decline near major put walls.
Between the call wall and put wall lies the gamma flip — the price level where total net GEX crosses zero. Above the gamma flip, positive GEX dominates and dealers trade against price moves (stabilizing). Below the gamma flip, negative GEX dominates and dealers trade with price moves (amplifying).
Breaking through the gamma flip with conviction is often the trigger for an accelerating move. A stock that slides below its gamma flip level can move 2-3x faster than it would in positive GEX territory because dealer hedging now adds fuel to the move rather than dampening it.
Unlike static technical levels, GEX walls shift as options positions are opened and closed. A call wall that exists at Monday's open may have moved by Wednesday as traders roll positions ahead of expiration. This is why monitoring GEX levels fresh each day — rather than relying on levels from prior sessions — is important.
The highest-GEX strikes tend to cluster around round numbers (e.g., 500, 750, 5000) because traders naturally gravitate toward those strikes when selecting options. This is why round numbers often "hold" as support or resistance even when there's no obvious technical reason — the GEX at those strikes is structurally higher.