An ascending channel is the statistically range bound price action of an ascending price trend contained between upward sloping parallel lines.
Higher highs and higher lows characterize the ascending/uptrend price pattern.
Technical analysts draw an ascending channel by manually drawing a lower trendline that connects the swing low pivot points, and an upper channel line that joins the swing high pivot points, or using a channeling drawing tool.
Some trading software or charting services can automatically plot ascending price channels.
