- 1). Measure one edge of the deck, where the vertical sides meet the horizontal decking. Mark that measurement on a piece of molding, with one mark about four inches in from the end and the second mark measured off that one. Put the marks along the back at the upper edge.
- 2). Stand the trim on your miter saw, as it will stand against the vertical sides of the deck. Slide it so one of the two marks is in front of the blade.
- 3). Turn the blade 45 degrees out, so it points toward the closest edge of the board. Make the cut.
- 4). Slide the trim to put the second mark under the blade. Turn the blade 45 degrees in the opposite direction, to against point outward. Cut it.
- 5). Hold the trim to the side of the deck, so the top of the trim is even with the floor of the deck. The two cuts should angle out at a 45-degree angle from both edges. Secure it there with a trim gun, with two nails (top and bottom of the trim) running every foot or so along the whole length of it.
- 6). Repeat for each remaining side of the deck, securing them in the same way, with the mitered ends pressed together to form the corners.
- 7). Caulk all around each of the trim pieces, putting beads wherever they meet the deck and the column.
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