Call wall
Also called gamma wall, resistance strike
The call wall is the strike above the current price carrying the largest modeled dealer gamma from call open interest.
In more detail
Large call open interest concentrated at one strike gives dealers a lot to hedge around that price. As the underlying approaches it, hedging flows can slow the advance, which is why the level is often described as resistance.
It is a description of where hedging concentrates, not a barrier. Price moves through call walls regularly, particularly when the underlying open interest is rolled or expires.
How Hermes measures it
Hermes computes the call wall from the same option-chain snapshot as the rest of a ticker’s gamma profile and states it on the ticker’s public page alongside the put wall and the flip.
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