To build a deck railing, secure rail posts to the corners of the deck and the middle of each side, and then attach 2-inch by 4-inch boards between each post to act as the top and bottom rails. Use a 2-inch by 6-inch board as a rail cap.
- Cut the handrail posts
Determine the height you want each handrail post to be. Add 9 inches to that measurement, and then subtract 1 1/2 inches. Cut each post to that length.
- Cut a notch in the handrail post
Use a circular saw to cut a notch that is 9-inches high and 2-inches deep at a bottom corner of the handrail post.
- Attach the post
Slide the notch over the corner of a deck beam, and secure it with bolts.
- Determine where the middle post must go
Measure the distance between the post and the next corner over of the deck. Divide the measurement by two, or divide by three if the measurement is more than 8 feet.
- Trace an outline
Trace an outline for the post at that spot on the surface of the deck. The post must fit in a way that makes the outside face edge level with the face edge of the deck.
- Cut and attach the middle post
Use a jigsaw to cut out the outline on the deck, and then use a circular saw to cut out the notch on the post. Bolt the post to the deck.
- Cut the rails
Measure the distance between each post, and cut the top and bottom rails to this size.
- Attach the bottom rail
Screw the bottom rail between the posts above deck level.
- Attach the top rail
Screw in the top rail so the surface of the rail is level with the surface of the posts.
- Add more railings
Repeat the procedure until every rail is up.
- Cut rail caps
Measure each side of the deck from corner post to corner post. Cut each rail cap to this length, and cut a 45 degree angle at each corner.
- Install each rail cap
Screw each rail cap into the tops of the rail.