A parapet comprises a plurality of uprights affixable to a substrate and a plurality of rails supported by the uprights, each rail being formed from a plurality of lengths of substantially equiaxed box section affixed to the uprights at a point along their length and joined end to end at locations between uprights. A suitable cross-sectional aspect ratio is less than between 1.4 and 1.1. The preferred external dimension of each side of the box section is between 60 and 90 millimetres, and the application also relates to such a rail per se. In a further aspect, the application describes a parapet comprising a plurality of uprights and at least one rail supported by the uprights, the uprights and rail being formed of steel and connected via bolts of stainless steel. It is preferred that the uprights and rails are galvanised. This avoids the requirement to touch up the bolts and any other fastenings with zinc paint in order to provide continuous galvanic protection to the entire structure.