A♥J♥ BB vs BTN, turn on Q♠ 9♦ 4♣ 2♠, 80 bb

Best play: Raise

Why

The 2♠ turn on Q♠9♦4♣ is a blank, but A♥J♥ holds strong backdoor-driven equity: it is ace-high with a gutshot, since a Ten gives A‑K‑Q‑J‑T... in practice the King-Ten window means you carry overcard outs plus the nut blocker that the Ace gives you against value Qx and AQ. From out of position you can check‑raise as a semi-bluff: you block the BTN's strongest Queens and Aces, you have a backdoor flush and the broadway gutshot picking up, and the fold equity against his missed barrels plus the outs when called make raising more profitable than passively calling ace-high. The Ace also blocks his check-back-then-bet value, so pressure here folds out better hands and sets up barrels.

Key idea

Ace-high with the nut blocker, overcards, and backdoors out of position prefers a check‑raise semi-bluff over a passive ace-high call.

Common mistake

Passively calling with ace-high lets the in-position bettor barrel you off your overcard equity and wastes the nut-blocker fold equity.