The upside gap 2 crows candlestick pattern is a bearish three candle pattern signaling the reversal of an uptrend.
The first candle should be a large full body bullish candle.
The second candle is important, and should be smaller bearish candle that gaps to the upside. The open of this candle should gap up away from the close of the bullish candle.
The third candle is no different for the 2 crows pattern. The open of the third candle should gap up from the close of the second candle but still move further down to make a lower close than the second candle, engulfing it completely.
The last two candles are considered the 2 black crows, and while it is preferred to have the third candle open above the second, it is fine for the open of the third candle to be located at the open of the second candle.
It is also important that the close of the third candle be located above the body of the first bullish candle. This leaves a partial gap unfilled with a close.