Call wall / put wall

A call wall or put wall is a strike where the options chain has an unusually large concentration of gamma exposure, large enough that dealer hedging around that specific price level dominates the flow. A call wall sits above the current price, built mostly from heavy call open interest at that strike. A put wall sits below it, built mostly from heavy put open interest. Both are read off the same GEX-by-strike profile used to find the flip line, just looking for spikes rather than the sign change.

The read is directional in a specific way. A call wall tends to act like a ceiling, since dealers hedging their short call exposure sell into any approach toward that strike, and a put wall tends to act like a floor, for the mirrored reason on the put side. The bigger the concentration relative to the rest of the chain, the more forceful that effect tends to be intraday, and it strengthens as expiration gets closer and the gamma at that strike gets larger per contract.

A wall is a tendency, not a hard limit. Price pushes through walls regularly, especially on a strong catalyst or once options open interest at that strike rolls off after expiration. Walls also shift from day to day as new strikes get added to the chain and older ones expire, so a wall that mattered last week can be gone by Friday. And a wall only describes dealer hedging flow. It says nothing about the buying or selling pressure from the underlying stock itself, which can simply overwhelm it.

Picture a stock at 118 with a call wall at 120 and a put wall at 112. Through most of the session, rallies toward 120 tend to stall as dealers sell into the approach, and pullbacks toward 112 tend to find buyers for the same hedging reason: the stock effectively chops inside that 112 to 120 band. If earnings beat expectations after the close and the stock gaps to 124 the next morning, it has cleared the call wall outright. The level that contained it the day before no longer applies once the catalyst is large enough to push through it.