In the image on the left you can see that the volume point of control (purple line) is present in the high volume node near the 15,605 level, however a second node has begun to build at the bottom of the range in the value area low (shaded purple histogram)
What can be seen in the video below and on the right hand image is that the volume builds to a point at which the volume profile flips, with the VPOC now towards the bottom of the range and the value area (blue) at the bottom of the range rather than the top. A bearish signal as the market is expected to return to VPOC which is now sixty points lower.
In this instance the market sold off by nearly 150 points following this flip
For more on volume profile check out this article, an overview of the volume profile indicator or click the tag below this article
I use the volume profile indicator by Volume Profile Solutions who have offered excellent support for the product following my purchase