A trendline acts as a resistance when it is drawn by connecting lower highs in a downtrend, showing the zone where selling pressure repeatedly enters the market. Each time price moves up and touches this falling line, traders often see it as an opportunity to sell, causing the price to face rejection again. The more times price respects the trendline, the stronger that resistance becomes. If price finally breaks above the trendline with strong volume, it can signal weakening bearish momentum and the possibility of a trend reversal or fresh upside move.