This indicator will draw the Parabolic Support and Resistance levels and then delete if older than your selected bars. The turn is calculated on above/below opens not closes as that seems to get most of the turns and this makes it slightly different than just the dots from a programming point of view.
For those who wish to see a video showing this indicator in use with Bollinger bands. You can watch the video here>>. Parabolic S&R Levels Video.
Very basically, the more previous crosses in bars past that are close together show the strength of the resistance/support level. I have noticed that price tends to want to break into clear ground which is easy to see as a clear chart area.