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Dealer Flow
Open Interest at a Strike: How It Builds the Call Wall and Put Wall
The walls aren't drawn on a whim — they're built from open interest. Understanding OI is understanding where the levels come from.
NoVo Options Trading · 2026
Open interest (OI) is the total number of option contracts currently outstanding at a given strike — positions that have been opened and not yet closed. It's not daily volume; it's the standing pile of contracts dealers have to hedge. And that hedging is what turns a strike into a level.
From open interest to a wall
When a strike carries huge OI, dealers on the other side hold a large, concentrated gamma position there, and they hedge it by trading the underlying. That hedging flow pins and defends price around the strike — which is exactly what a call wall or put wall is. The wall is the market's footprint of where the most open interest (and therefore the most hedging) sits.
OI vs volume
Don't confuse the two. Volume is how many contracts traded today; open interest is how many are still open. A strike can have a busy day of volume that all closes out, leaving little OI — or quietly accumulate OI over days into a major level. For structure, OI is the number that builds the walls; volume just shows today's activity.
Volume is today's noise. Open interest is the standing structure — the pile of hedging that draws the walls.
The nuance: not every big OI strike is the wall
Raw OI is a clue, not the whole answer — what matters is the gamma that OI represents, which depends on the strike's distance and the option type. That's why a proper dealer map weights OI by gamma rather than just flagging the biggest number (see how to read dealer positioning). NoVo computes the walls from the gamma-weighted picture, so the level you see reflects real hedging pressure, not just a large open-interest headline.
More on this: How Skew Shows Up in the Put Wall's Position · Why the Biggest Open-Interest Strike Isn't Always the Wall · Calculating Break-Even on a Long Call or Put · Call Wall vs Resistance: What's the Difference?
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NoVo is a software tool for market analysis and for executing trades you initiate, not financial advice. This article is general education, not investment advice. Options trading involves substantial risk of loss, up to and including your entire capital. NoVo makes no guarantee of profit, win rate, or performance, and past results do not predict future outcomes. You are responsible for your own broker account, configuration, and trading decisions.