Guard rail or guardrail, sometimes referred to as guide rail

Guide rail

A Guide Rail is a system designed to guide vehicles back to the roadway and away from potentially hazardous situations. There is a legal distinction between a Guide rail and a Guard rail.- Guide Rail Types :...

 or railing, is a system designed to keep people or vehicles from (in most cases unintentionally) straying into dangerous or off-limits areas. A handrail

Handrail

A handrail is a rail that is designed to be grasped by the hand so as to provide stability or support. Handrails are commonly used while ascending or descending stairways and escalators in order to prevent injurious falls. Other applications include bathroom handrails—which help to prevent falls on...

 is less restrictive than a guard rail and provides both support and the protective limitation of a boundary.
Most public space

Public space

A public space is a social space such as a town square that is open and accessible to all, regardless of gender, race, ethnicity, age or socio-economic level. One of the earliest examples of public spaces are commons. For example, no fees or paid tickets are required for entry, nor are the entrants...

s are fitted with guard rails as a means of protection against accidental falls.