Walls

Walls are prices where market makers' hedging tends to push back. The call wall (green, above the price) tends to slow rises; the put wall (red, below) tends to cushion drops. Each line shows the wall price and its distance from today's price.

Where they come from

Walls sit at the option strikes with the most gamma — where the largest amount of open options make market makers trade the most stock as the price gets close.

Call wall — the strike with the most call gamma. As the price rises toward it, hedging tends to sell.
Put wall — a strike with a large share of put gamma (at least 15%), preferring the one closest at or below the price, so a far-away crash hedge does not win on size alone. As the price falls toward it, hedging tends to buy.

Reading a line

~3 90.5 (+6.2%) · 87.3 (−4.2%)

~10 90.5 (+6.2%) · 87.3 (−4.2%)

~31 95.0 (+11.5%) · 85.0 (−6.8%)

One line per expiration: Nearest (dot), Next (line), Horizon (square).

~10 — days until that expiration. The mark after it is how that expiration is drawn on the chart.
90.5 (+6.2%) — the call wall, 6.2% above the price.
87.3 (−4.2%) — the put wall, 4.2% below the price.

— means that expiration had no usable data.

On the chart

The same walls, right of the last 45 days: a short tick at each expiration, joined per side by a dashed line — call walls above, put walls below. The space between ticks follows the days to expiration.

When walls hold — and when they don't

Walls are strongest when hedging damps moves, above the gamma flip. Below it, a wall is drawn faded: hedging there adds to moves, and walls are more likely to be run through.

Limits

Walls come from yesterday's open interest, repriced at today's price. They shift as options open and close.
The dashboard reads strikes within a set range of the price (see Asset class); the X-Ray reads the whole expiration.
A wall is a price where pressure is likely, not a promise that the price stops there.