Deck railings must conform to certain minimum standards, and building codes are very specific about these standards. Railings also need to be strong, as they are subject to extreme lateral forces. Vertical members, such as posts, often must act as levers to concentrate significant loads directly on the bolts holding the railing together. Most traditional railings have posts for support, with horizontal rails and numerous smaller vertical balusters. The top rail may be composed of several parts, in which case the uppermost piece is called the cap rail.
Railings often have a bottom horizontal rail.
If you want to move away from traditional railings, the large intermediate posts can be eliminated and the railing can rely on balusters lapping the rim for support. Another design option is for the posts to be only vertical members, with the intermediate spaces filled with horizontal rails.