Highs and Lows are crucial while drawing trend-lines as responsible buyers or sellers step-in at those prices causing it to be Highs and Lows, so, wicks! Automatic Trendline AFL.
Personal suggestion: If you are interested to get rid of indicators and purely delve into price-action, trend-lines, channels or patterns, would suggest you to read Suri Duddella's Trade Chart Patterns Like the Pros: Specific Trading Techniques. The author has consolidated and meticulously explained several Technical Analysis topics comprehensively..