A P&F Long Tail Down Reversal is a column of X's that follows an unusually long column of O's, often 20 boxes or more. Point and Figure charts plot rising prices as columns of X's and falling prices as columns of O's, ignore time, and add a new column only on a reversal of several boxes, which filters out minor moves. A steep, uninterrupted decline often leaves the stock oversold, so the first reversal up after it can mark a sharp rebound.