Turtle EXIT STRATEGY

"The System 2 exit was a 20 day low for long positions and a 20 day high for short positions. All the Units in the position would be exited if the price went against the position for a 20 day breakout." [1]


QUESTION:

HOW DO I KNOW WHEN THE PRICE GOES AGAINST THE POSITION FOR A 20 DAY BREAKOUT USING (AROON 20) INDICATOR?




Reference:
[1]http://www.elliottgann.com/en/index.php/Chapter_VI_-_Exits