Trendlines: The Rule of Three Touches
Learn how to draw reliable trendlines, validate them with a third touch, and spot why steep lines fail quickly.
When you open a stock chart for the first time, it can look like a chaotic mountain range. Prices jaggedly rise and fall, leaving you wondering where the structure is. But if you connect the price lows with a single straight line, order suddenly emerges. This line is a trendline. It is one of the simplest tools in technical analysis, yet it is incredibly powerful because thousands of other investors are looking at the exact same line.
The Rule of Three Touches
To draw an upward trendline, you look for the low points where the price stopped falling and turned back up. However, you cannot just draw a line through any two points and call it a trend. There is a strict rule of validation that you must follow to avoid false signals:
- Two touches make a draft: You can draw a straight line through any two random points on a chart. At this stage, the line is just a tentative guide. It has no proven authority.
- Three touches make a trend: When the price falls back to your line for a third time and bounces off it, the line is validated. This third touch shows that the market actively recognizes this line as a support level.
How to Calculate a Trendline
Let us walk through a simple, paper-and-pencil calculation to see how this works mathematically. Imagine a local paint manufacturer, ABC Paints, whose stock is steadily climbing.
- Step 1: Identify Touch 1. On Day 1, the stock hits a low of ₹100 and bounces up.
- Step 2: Identify Touch 2. On Day 11, the stock dips to a low of ₹110 and bounces up again. You connect these two points.
- Step 3: Find the daily growth rate. Subtract the first price from the second (₹110 - ₹100 = ₹10) and divide by the number of days between them (10 days). The rate of ascent is ₹1 per day.
- Step 4: Predict the third touch. If the trend continues, on Day 21 (10 days after Touch 2), the trendline value should be: ₹110 + (10 days x ₹1) = ₹120.
- Step 5: Validate. If the stock dips to exactly ₹120 on Day 21 and bounces upward, your trendline is validated by a third touch.
Channels and the Danger of Steep Slopes
Once you have a validated bottom trendline, you can often draw a parallel line across the peak highs. This creates a channel. Channels are highly useful because they give you a visual corridor, showing you where the price is likely to find resistance at the top and support at the bottom.
As you draw these lines, pay close attention to their slope. Steep trendlines are like fast cars on sharp turns—they look exciting, but they crash easily. A line with a steady 30 to 45-degree angle is sustainable and can last for months. A line steeper than 60 degrees is almost guaranteed to break quickly. A stock price cannot rise vertically forever. When a steep trendline breaks, it does not always mean the stock is going to crash; it often just means the price is returning to a healthier, gentler slope.
Always wait for a third touch to validate a trendline before making decisions, and treat steep trendlines above 60 degrees as temporary phases rather than permanent trends.
You can practice drawing these lines and spotting channels using the interactive charting tools on any stock's analysis page on stock-analyze.com.