Trim the Excess
After you've nailed all boards into place, come back and run a straight line across the excess out boards. Make sure and allow for any trim moldings that may go under the front of the porch. Using a jigsaw, cut off the excess wood. This will provide a straight edge for finishing (Image 1). Use a router to round the edges on the top and the bottom (Images 2 and 3). Sand the edges smooth, then prime and paint (Image 4). Always remember to prime raw wood before painting the finish coat.