The Hanging Man candlestick formation, as one could predict from the name, is viewed as a bearish sign. This pattern occurs mainly at the top of uptrends and can act as a warning of a potential reversal downward. It is important to emphasize that the Hanging Man pattern is a warning of potential price change, not a signal, in and of itself, to go short.
The Hanging Man formation, just like the Hammer, is created when the open, high, and close are roughly the same price. Also, there is a long lower shadow, which should be at least twice the length of the real body.
When the high and the open are the same, a bearish Hanging Man candlestick is formed and it is considered a stronger bearish sign than when the high and close are the same, forming a bullish Hanging Man (the bullish Hanging Man is still bearish, just less so because the day closed with gains).
After a long uptrend, the formation of a Hanging Man is bearish because prices hesitated by dropping significantly during the day. Granted, buyers came back into the stock, future, or currency and pushed price back near the open, but the fact that prices were able to fall significantly shows that bears are testing the resolve of the bulls. What happens on the next day after the Hanging Man pattern is what gives traders an idea as to whether or not prices will go higher or lower.