Double Bottom Reversal
The double-bottom pattern is found at the bottom-most trough of a down trend and is a clear signal that the preceding down trend is weakening and that sellers are losing interest. Upon completion of this pattern, the trend is considered to be reversed and the security is expected to move higher.
As with the double top chart pattern the double bottom pattern usually forms over the intermediate to long-term (1 month onwards). It can be found in other circumstances though after a trend. It's never found in a range. Everything we've talked about for the double top pattern applies to the double bottom chart pattern, only in reverse. The below chart of MXB shows the double bottom pattern. You'll see that the second trough doesn't quite hit support, but it's still a valid pattern.
Further reading on the double bottom reversal can be found under Mod 6. Trading Psychology - The "Shake-out". You'll get further perspective on the psychology involved with this chart pattern