I never get tired of this set-up - I see it many times every day across any number of time periods. Here it is on the daily charts with REGN. I've annotated a couple of spots - first the basic set-up is minimum of two days down with increasing volume on the second day. This example has the added feature of having some significant volume which just adds to the probability of a happy ending. Then the third candle is up with the low of the day being higher than the low of the previous day.
That's all there is to it. If you use the BOB method you can make the buy anywhere at "a" or above (recommended - not mandatory) and set your stop at "b" or below (suggested - not mandatory).
Any number of software filtering packages that allow you to "roll your own" will enable you to find good old BOB - I use stockfetcher.com.
Of course if you are still using the prepackaged filters at MSN money dot coma you won't find BOB but to each his own.