Since over 200 pounds of tension is being applied to end posts using cable railing, those posts must be substantial enough to handle that tension.
For wood posts a minimum 4x4 (3½”-square) post is required to keep the post from bending when the cables are tensioned. You will need a top rail, and we recommend that it be reinforced with a support such as a 2x4 on end under the top rail.
End posts must be securely mounted to the deck to prevent the post from coming loose when the cables are tensioned. A bottom rail helps distribute the force away from the bottom of the post, but is not required.
To keep the cable from spreading beyond IBC code requirements, we recommend that the cable be supported in some manner no more than every 48” along its run. Intermediate posts, through which the cable is strung, act as supports for the cable. To avoid having to use more intermediate posts than is structurally necessary, a thin metal cable brace with holes for the cables to pass through can be used to support the cables (see illustrations). A typical cable brace is either 3/4” x 3/4” aluminum tube or 1/4” thick by 1” wide stainless steel flat bar and is ordered separately.
We recommend that you space the cables with no more than a 3” clear span between the cables (see illustrations). For example, if you are using 1/8” diameter cable, you would drill your holes on center no more than 3-1/8” apart.