In common terms it is about the Support and Resistance Lines, but in PFT it is wider and refers to the reliability of the micro (local) graphical model. Example: scale 3 shows us sharp Amplitude Increase but lower tangent became unreliable and can't be Support Line (and market confirms it by easily penetration through that line). But at scale 4 lower tangent is more reliable and may be a boundary of the real channel. In general words, the last tangent in configurations with Amplitude Increase can't be a good estimation for the channel. (Full version of the article about Price Flow Theory and Price Flow Analysis will be posted in "Technical Analysis" soon).