Trendlines: How to Draw Them Honestly and Why Breakouts Are Often False

A trendline connects successive lows (in an uptrend) or highs (in a downtrend). It's a visual description of direction. Its weakness is simple: at the right edge of the chart nobody knows which lows are the “right” ones, and the line is easy to redraw after the fact.

What it is

Classic technical analysis requires at least two points to draw a line and a third to “confirm” it. The slope, the chart scale (linear or logarithmic) and the choice of wicks or candle bodies all produce different lines.

A break of the line is treated as a signal of a trend change, and a retest from the other side as confirmation.

How people use it

buying at an uptrend line
a line break as a reversal signal
trend channels with a parallel line

What the research and evidence say

Lo, Mamaysky and Wang (2000) showed that some price patterns may carry additional statistical information, but their work required objective, algorithmic identification of the shapes. Hand-drawn lines are subjective, so they're hard to test properly. A typical mistake is judging trendlines on charts where they “worked”.

Weaknesses

subjective choice of points
the chart scale changes the line
lines get redrawn when price crosses them
a breakout without volume often falls back

What order flow shows

When price reaches a trendline, order flow lets you check whether demand appears there: whether aggressive selling weakens and gets absorbed, or passes through the level without resistance. On a breakout you can see whether the market accepts the new prices on the other side or quickly comes back, leaving traders trapped.

Indicators vs order flow

Every indicator and every pattern in this section is built from the same data: a candle's open, high, low, close and sometimes volume. They're derivatives of price, showing the effect rather than the cause. Order flow looks at what price is made of: who was buying and selling aggressively (delta), where limit orders were waiting (the order book) and at which prices the market accepted trade (the volume profile).

On CME futures this data is real and comes from one central market. Spot forex doesn't have it: platforms show tick volume, the number of price changes at a single provider.

To be fair: order flow isn't the Holy Grail. It takes learning, it can be noisy, big players hide some of their orders, and an edge only comes from a process and risk control. But it gives you information that simply isn't on a candlestick chart.

How to use it sensibly

set your drawing rules before the analysis and stick to them
don't redraw the line after a break – just note that it was broken
judge a breakout by acceptance and volume

Glossary: Support and resistance
Glossary: Trapped traders
Glossary: Acceptance and rejection
Atlas of biases: Hindsight bias
Atlas of biases: Belief perseverance
Order flow: How to read charts from a real market
Also under the microscope: Fibonacci retracements
Also under the microscope: Support and resistance
Also under the microscope: Pivot points

Frequently asked questions

How do you draw a trendline?

In an uptrend you connect at least two rising lows, in a downtrend two falling highs. It's worth setting the rules for choosing points in advance.

What does a trendline break mean?

That price has moved outside the existing angle of the move. It doesn't automatically mean a trend change, especially without volume and acceptance of new prices.

Educational content, not investment advice. No signals, entries, stops or position sizes.