Pin Bar, which is short for ‘Pinocchio Bar,’ is a single candlestick setup that clues price action
traders into potential reversals in the market. A pin bar is an elongated wick that ‘sticks out’ from price action. Traders will usually look for one-sided wicks that are two times the size of the candlesticks body.
When traders see elongated wicks sticking out from price action, they can look for the momentum
that created the long wick to continue by looking for a reversal.
So if a trader sees a long wick sticking out below price action; they can look to go long. If a trader sees a long wick sticking out above price action, they may want to look to go short.
See also: http://www.forexschoolonline.com/pinbar/