You can find Jack's description of 2 pair in the attached 1-pager.
Previously in this thread I attached a screenshot of how the 2 pair and spike can be seen on a 1min chart with price axis set to tick increments. It may have been a month or two back and was in the context of an exchange of several posts with Makosgu.
If you keep in mind that price is always a pair, the 2-pair concept is simple to grasp. Some questions to ask might be: Where do 2 pair and spikes occur? Are all trend changes accompanied by 2 pair and spikes? Does every 2 pair and spike mean a trend change? How does the 2 pair and spike fit within the entire set of monitoring inputs?