Young Blonde Girl Behind The Guard Rail

Examples of this are both architectural and environmental. Environmental guard rails are placed along hiking trails where adjacent terrain is steep. Railings may also be located at scenic overlooks.
Guard rails in buildings are numerous, and are required by building codes in many circumstances. Guard rails along stairways are common, and catwalks and balconies are also lined with them.
Building codes also require that no opening in a guard be of a size such that a 4" sphere may pass. There are three exceptions according to the 2003 International Building Code Section 1012.3 which allow openings to not exceed 8" or 21" depending on occupancy groups or special areas.
An architect who was famous for creative use of handrails for social stability was Alvar Aalto. The guard rails of an observation tower such as the Space Needle or Eiffel Tower become exaggerated to the point of becoming a fence or cage. This is also done on bridges and overpasses to prevent accidents and suicides.