The put wall is the strike below spot with the heaviest put-gamma concentration. In a positive-gamma regime, it behaves like support — the downside bookend of the day's likely range, and a spot dips tend to bounce from.

Why the floor holds

The same dealer hedging that caps rallies at the call wall cushions declines at the put wall. As price dips toward it, positive-gamma hedging leans into the weakness — buying — which absorbs the move and pins price near the level. That's why the put wall is a high-quality bounce spot when the regime is calm: the flow is mechanically defending it.

The put wall isn't held by hope — it's held by dealer hedging buying the dip. Which is exactly why it fails when that hedging inverts.

The warning: when it fails

A decisive break of the put wall is one of the more dangerous events on the map. It often coincides with a cross below the gamma flip into negative gamma, where the cushioning hedging inverts into selling — and the level that was support becomes the doorway to a negative-gamma spiral. The floor doesn't just give way; it can turn into an accelerant.

How to trade it

In positive gamma, treat the put wall as a bounce zone — but define your invalidation at the wall. A dip that holds and reclaims is the bounce; a decisive close below it is not a “cheaper entry,” it's a regime warning to get out of longs and stop buying. Respect the floor while it's defended, and respect the break just as much — the whole edge is knowing which one you're looking at.