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I'll try a rough explanation. There's more to it like choosing box sizes etc.
Here's the XJO. The X's are demand (up) and the O's are supply (down). It's like a game of footy. One side has the ball and runs with it, then the other. The stronger one travels further and surpasses the other creating a breakout in a direction. I've used a box size of 50 points and a reversal of 3. That means it has to reverse 3 x box size or 150 points in the opposite direction to start a new column.
In Wyckoff, PnF is one way to measure cause and effect. I programmed this into my charting application to do it for me. The green vertical line and the red vertical line span some cause — a consolidation or trading range. The red horizontal line is the last point of supply and the green horizontal line is effect — the estimated price move. The XJO was almost there.
You can also use 45 degree lines to draw trend channels. Wyckoff wrote about it in his course. There are also some good books on it by Du Plessis or Dorsey.
Hope that helps.
