A chart construction with a main Trendline and a parallel boundary describes a selected price move. Here it means a manually or rule-anchored channel, not any indicator with bands.
StockCharts builds an ascending Price Channel on at least two reaction lows and a descending one on highs. The main Trendline thus determines the slope; anchor selection must form part of the method's description. [1]
StockCharts draws the second line parallel to the main one; an opposing price point can determine its position. Knowing the slope alone therefore does not establish the opposite boundary. [1]
TradingView allows the price and bar number of both base-line anchors and the price offset of the opposite boundary to be entered. Also retain the market, Timeframe and price scale for reproduction. [2]
StockCharts emphasizes price scale. On a linear axis a parallel channel has a constant price difference at the same time; on a logarithmic axis it has a constant price ratio. Do not confuse monetary width with percentage distance. [1]
TradingView allows the channel to be extended and levels to be added at a specified ratio. These are drawing settings; they do not supply a new price observation or prove that the market must react to an internal line. [2]
StockCharts distinguishes crossing different boundaries of ascending and descending channels. Before a test, specify the boundary, tolerance and whether intrabar movement is sufficient or Close is required; this is not a universal reversal rule. [1]
TradingView supports channel-crossing alerts with a condition and frequency. A triggered alert does not establish an available fill price, profit or order execution. [2]
TradingView's warnings about lookahead bias and overfitting imply a requirement to retain anchors known at decision time. Later channel widening must not retrospectively erase an earlier break; testing should include costs and slippage. [3]
Same slope, constant price width
For the clearest picture, read this entry together with Trendline, Support and Resistance, Technical analysis, Bollinger Bands, Breakout, Backtesting. The reverse links also lead from Just-in-Time Channels, Splicing.
01Is every indicator with two bands the same channel?+
No. This entry describes anchored parallel lines. Bollinger Bands, for example, use their own calculation; their variable width is not interchangeable with the fixed offset of this linear example.
02Can I widen the channel after a break?+
Yes, for a new chart description, but record the change and its time. When testing the original rule, a later adjustment must not erase a break that was valid against the boundaries known then.