This counts the number of up or down thrusts over the previous N days and creates a total (up thrust - down thrust) to produce the graph.
It also optionally will include "run days" as part of the same count.
The idea is that it gives you an indication of the strength of the current trend (and can possibly help you spot it reversing ;))
For more on thrust days...
Falcon highlights "Thrust Days"
A thrust day (as defined in Jack D. Schwager's book - A Complete Guide to the Futures Market: Technical Analysis, Trading Systems, Fundamental Analysis, Options, Spreads, and Trading Principles) is as follows:
"An upthrust day is a day with a close above the previous day's high, while a downtrhust day is a day with a close below...
