From roughly 3pm to the close, a same-day option's gamma is at its maximum, so the gamma effect intensifies — whatever the regime is doing, it does harder. The power hour isn't a single playbook; it's two, and the regime picks which.

Positive gamma: fade the pin

In a pinned, positive-gamma close, price magnetizes to big strikes and ranges compress. The play is to fade the edges of the pinned range back toward the magnet strike — sell pushes up, buy pushes down — and distrust breakouts, which mostly fail. Small, quick scalps into the pin, not swings.

Negative gamma: ride the break

In a negative-gamma close, hedging amplifies, and the last hour can produce the day's fastest move. Here you respect momentum — trade continuation, not reversion — because a pin that breaks late runs. Fading a negative-gamma power hour is how a calm day's small loss becomes a large one.

Same clock, opposite trades. Read the regime first — the power hour amplifies whichever one you're in.

The two hard rules

First, be flat before liquidity leaves: spreads blow out into the close, so your exit costs more the longer you wait. Second, never let an in-the-money 0DTE ride into settlement — it auto-exercises into shares. Many scalpers take the power-hour move and are done well before 3:55. NoVo's exit ladder banks winners on the way up, and a one-click close gets you out before the close, not into it.