Call wall and put wall: the session's boundaries (capture 3)

The call wall is the strike above price where call activity is most concentrated; the put wall is its counterpart on the put side, below price. Together, they often frame the session's range.

• Call wall: dealers are often long gamma there (clients selling covered calls). As price approaches, they sell more and more: price slows and struggles to hold above.
• Put wall: a zone where hedging buys the dip or, if dealers are short puts, where it can accelerate the drop. It has two faces: support or breaking point.