Abstract: A prefabricated flashing for post bases intended for installation in new or existing construction comprising two different pieces. One piece having a nailing flange (22) which fits snugly around a post whose dimension is 31/2".times.31/2" has a total of eight nail holes (20) and has four tapered sides (28) that terminates in a bottom flange (29). The second piece is shaped and sized similarly to the first except that it is split verticaly straight across the nailing flange and on one side has an extension of material (30) which creates a seam.