Trendline as support and resistance level

Trend line can act support and resistance level. Most of trader will use support level for BUY entry and resistance level as a SELL entry.

Support

Support is defined as a price has difficulty to break below, and is so named because it supports or holds up the price. Trend lines show potential support by the extension of the trend line into the future. Support is most often shown by upward trend lines, but can also be shown by sideways trend lines. A strong trend line will keep the price above the trend line and its associated support, until the support weakens, at which time the price will break through the trend line, and trade below the trend line and its associated support.

Resistance

Resistance is defined as a price has difficulty to move upward, and is so named because it resists or holds down the price. Trend lines show potential resistance by the extension of the trend line into the future. Resistance is most often shown by downward trend lines, but can also be shown by sideways trend lines. A strong trend line will keep the price below the trend line and its associated resistance, until the resistance weakens, at which time the price will break through the trend line, and trade above the trend line and its associated resistance.

At example above, when price break the DTL actually market giving a signal they will change the move, in this case market will make u turn and go upward. Its clearly show as long as the market hold the DTL, you can keep your SELL trade but beware if price break above the DTL you should consider to take your profit or cut loss your trade.

Usually we using dtl or utl as our emergency exit line.