When the confirmation line of a Head & Shoulders pattern breaks to the downside, a large amount of volume should occur as well.
The chart below of General Electric (GE) shows a sharp increase in volume when the confirmation line of the Head & Shoulders pattern was broken:
In addition to the sharp increase in volume, the gap down on the chart of GE also gave strong indication to sell when the confirmation line was pierced.
The same concept applies to a Reverse Head & Shoulders pattern, the break of the confirmation line should be accompanied by an increase in volume.
The chart below of Gold futures illustrates a rise in volume when the confirmation line was pierced:
The Head & Shoulders pattern is a highly effective classic charting pattern. Other similar chart patterns are the Double Top formation (see: Double Top) and the Double Bottom formation (see: Double Bottom).