A stop-loss placed at a price level where the original trade thesis is invalidated by market structure — not at an arbitrary fixed distance from entry. Examples: for a stacked-imbalance short, the stop sits one tick above the highest level of the zone (if price trades through, the imbalance creators were overwhelmed); for a trapped-buyer short, the stop sits one tick above the trapped high. Structural stops are typically tight, producing the favourable risk-to-reward ratios that make order flow setups viable.