Check with your local building department to ensure that the codes in your municipality allow for horizontal deck railings.
Measure the total length of the railing you’ll need and add 2 feet to calculate the total cable length. Determine the number of cables you’ll use in the railing, allowing one for every three inches of post height. Order the cable along with the necessary hardware such as protector sleeves, self-locking fittings and end caps, as well as any tools specified by the cable manufacturer for installation.
Reinforce the end posts as necessary to ensure they can tolerate the stress of the tightened cables. End posts should ideally be 4-by-6 lumber, or secured through a beam or joist with four 1/2-inch lag bolts, washers and nuts.
Drill 1/4-inch cable holes in all the posts by clamping a template to the side of the post and drilling through the holes. If the cable system you purchased did not come with a template, create a drilling template by drilling holes spaced 3 inches apart in the face of a 2-by-4. The board should be cut to match the spacing between the top and bottom rails, if any, or between the deck and the top of the post.
Drill 5/16-inch holes in the first post to match the diameter of the threaded rods on the starting end of each cable. Use a 3/8-inch bit to counter bore the outside of the last post.
Insert the threaded rod for the first cable through the middle hole on the first post on the railing side. Secure it on the other side with the supplied washer nut. Tighten the nut snugly, but not completely.
Thread the other end of the cable through the middle holes in each succeeding post. If your cables came with rubber grommets, thread the cable through each grommet and then into the post hole, pressing the grommet into place.
Tap a protector sleeve into the hole in any post where the cable must be routed around a corner or at an angle.
Slide a self-locking fitting over the cable end as you feed it through the outside hole in the final post. Snug the fitting down into the counter-bored hole.
Hold the extra cable that sticks out from the self-locking fitting with a pair of pliers. Slowly and evenly pull the cable tight while holding the fitting in place. When the cable is tight, cut the end flush with the outside edge of the self-locking fitting.
Tighten the washer nut on the starting post’s threaded rod, using a 7/16-inch box-end wrench and holding the other end of the rod with pliers to stop it from turning.
Cut off any threaded portion that projects out beyond the nut, using a hacksaw. Grind the nub down if necessary, and cover the nut with a snap-on end cap. Repeat the process, running one cable above and one cable below the strung cables, until all the remaining cables have been installed.