Well, I'm certainly not the master of this technique, but if you're ever on Twitter search for @Bangontrader to get more examples (he/she really is incredible when it comes to this technique).
Effectively, I would say that the technique is about the extrapolation of longer term trend lines (although it works on short time frames too). The idea really is that where these trend lines meet you get a pivot point (so in the above example, I would expect a bullish reversal at the confluence of lines at ~157).