A trendline support zone is an area on a price chart where an upward-sloping trendline connects multiple swing lows, indicating a zone (not an exact line) where buying interest consistently emerges. When price pulls back toward this zone, buyers tend to step in, absorbing selling pressure and pushing price higher, which helps maintain the ongoing uptrend. The more times price respects this support zone and rebounds from it, the stronger and more reliable it becomes, often acting as a reference point for low-risk buying, stop-loss placement, and trend confirmation.