How to read this: Each bar is the net dollar gamma dealers carry at that strike for today's expiration only (0DTE), scaled to a 1% index move — green where calls dominate (net long gamma), red where puts dominate (net short gamma). The blue line is the aggregate (cumulative) gamma across strikes; where it crosses zero is the gamma flip: above it dealers are net long gamma, so hedging leans against price (dampening moves, encouraging pinning); below it they're net short, so hedging chases price (amplifying moves). The call wall — the largest positive-gamma strike above spot — often caps rallies, and the put wall below spot often cushions dips, though a decisive break below it can accelerate selling. 0DTE gamma on SPX and NDX is dominated by dealer flow and can shift fast intraday — refresh often.