An ascending trendline is simply a diagonal trend-line drawn over a chart to connect a series of higher highs or lower highs.
Ascending trend lines are plotted overbullish trending markets to determine where the price action is likely to go if the trend continues uninterrupted. These bullish trendlines are also used to indicate possible breakdowns in the prevailing direction.
If price action breaks below an ascending trendline, it can be a bearish signal. As with all other trend lines, when the price is trading above them, they are regarded as support, and when the price is trading below them, they are seen as resistance.