The piercing pattern often will end a minor downtrend (a downtrend that often lasts between five a  fifteen trading days) The day before the piercing candle appears, the daily candle should ideally have a  fairly large dark real body, signifying a strong down day. In the classic piercing pattern, the next day’s  candle gaps below the lower shadow, or previous day’s low.

In order for the Piercing signal to be valid, the following conditions must exist:

·The stock must have been in a definite downtrend before this signal occurs. This can be  visually seen on the chart.
·The second day of the signal should be a white candle opening below the low of the previous  day and closing more than half way into the body of the previous day’s black candle

Example