Regardless of the height of the outdoor wooden steps, adding a hand rail will provide added safety. Because the railing is intended for outdoor use, treated posts and 60 cm x 90 cm (2 x 4 foot) lumber holds up better than non-treated wood in the elements. The materials necessary for construction are available at most hardware and home improvement shops. Consider obtaining the help of an assistant for cutting and constructing the hand rail.
Locate the centre of the top step portion of one stringer board by using a tape measure and straightedge. Measure the horizontal and make a pencil line, then measure the vertical and make a line. On the vertical line, measure 3.8 cm (1 1/2 inches) up from the centre point and make a mark, and then equally down 3.8 cm (1 1/2 inches) from the centre and make another mark. Drill holes through the upper and lower marks using a 1.3 cm (1/2 inch) wood bit.
Measure, mark and drill identical holes on the lower step portion of the same stringer as in Step 1. Repeat the entire process on the opposite stringer at both the top step and bottom steps, so that a total of four holes are on each of the two stringers.
Cut two 10 cm x 10 cm x 1.8 m (4 x 4 inches x 6 feet) posts in half with a circular saw. Lay the four posts out on sawhorses. Measure 5 cm (2 inches) up from the bottom of all posts and make a mark at the centre of each post. Measure 7.5 (3 inches) further up and make another mark. Drill 1.3 cm (1/2 inch) holes through the posts at the marked areas.
Hold one of the posts at the top of one stringer and align the holes. Slide two 15 cm (6 inch) long, 1.3 cm (1/2 inch) diameter bolts through the holes. Place metal washers on both sides of the stringer board and tighten the bolt and nut down completely with a socket wrench. Repeat the insertion of bolts for all posts.
Measure 15 cm (6 inches) down on the downward facing side of each post and mark it. Use a sabre saw to cut the posts so they angle down the same as the 45 degree angle of the step stringer. Measure the distance from the longest edge of the high post down to the low side of the bottom, same-side post.
Cut a 5 cm x 10 cm (2 x 4 inches) railing board to fit the previously measured distance between posts. Align the board so the 10 cm (4 inch) side is laying flat against the tops of the posts as a cap. Drive four 9 cm (3 1/2 inch) deck screws down through the railing and into each of the posts to anchor it. Repeat for the other side of the steps.
Have an assistant to help hold or brace pieces when mounting them together.
Round the edges of the railing with sandpaper to make them smooth and avoid accidental injury. Use proper precautions and eye protection when using power saws and drills.