Node-locking is an advanced solver feature that allows the user to fix one player’s strategy at a specific game tree decision node to non-equilibrium frequencies, then observe how the opponent’s optimal strategy adjusts in response. This technique is extremely useful for studying exploitative play, as it simulates situations where an opponent makes specific mistakes such as never bluffing on the river or always c-betting, revealing the EV-maximizing response. Node-locking also analyzes how small equilibrium deviations propagate through the decision tree.