Call wall
The strike that holds more call gamma than any other strike nearby. Traders watch it as a level where dealer hedging may lean against a move higher.
A call wall is the strike where call open interest and gamma combine into more call gamma exposure than at any other strike nearby. If dealers are long those calls, as GEX models usually assume, they sell into rallies toward that strike to stay hedged, which is why the level is watched as possible resistance.
Walls are model outputs, not barriers. A large position at one strike can be a single trade or a hedge, and the wall can shift or disappear when those options expire. On a net GEX chart such as CaymanBot's, the tallest positive bars play the call-wall role.
Illustrative example (hypothetical numbers, not a real trade): the 105 strike carries 40,000 calls with a gamma of 0.03, against no more than 10,000 calls at any nearby strike. Its share-equivalent gamma is 40,000 × 0.03 × 100 = 120,000 shares per $1 move, which makes 105 the call wall.