If the price breaking up through resistance and making a new higher peak is a buy signal, then the reverse must also be true.

When the price breaks down through the support line and makes a new lower trough, then you have a strong SELL signal. This will occur when the stock goes directly from an ascent phase into the descent phase, bypassing the distribution phase. This is a rare occurrence as there is normally at least a brief distribution phase, but can occur if market sentiment turns very quickly from bullish to bearish. An example of this can be seen below.

We can line up a number of troughs in this medium term trend and this forms the support line.

Zooming in closer …

The price breaks down through the support line but is still above the previous trough. Confirmation comes when the price closes lower and begins to form a new lower trough.