Rails

A 6-foot fence should have three rails — top, middle, and bottom. Three rails provide the structural rigidity to prevent boards from bowing, rattling, or being pushed in. Some budget installations use only two rails on 6-foot fences, but this reduces stiffness and typically results in board movement and faster wear at fastener points.

Rail material varies by fence type. Wood fence rails are typically 2x4 or 2x3 cedar or pressure-treated lumber. Chain link top rails are round galvanized steel pipe. Ornamental steel fence rails are square or rectangular tubular steel welded or fastened to the pickets. Vinyl fence rails are hollow extruded PVC profiles that the pickets slide into.

Wood rails break or sag due to rot at fastener points or end cuts, insufficient sizing for the span, or physical impact. In ornamental steel and chain link, rail failure typically results from vehicle impact, severe weather, or corrosion over time. Three-rail configurations reduce sag risk by shortening the unsupported span of each board or picket.