Final answer:
The height of a guardrail and the required number of rails depend on specific building codes and safety regulations. These can vary by location, but in the U.S., OSHA stipulates a minimum of 42 inches for guardrail height and typically includes a top rail, mid rail, and sometimes a bottom rail.
Step-by-step explanation:
The question regarding the height of a guardrail and the number of rails each one must have depends on various building codes and safety regulations, which can differ by locality, type of road, and specific use case. For example, in the United States, the Occupational Safety and Health Administration (OSHA) requires guardrails on open sides of walking surfaces that are 4 feet or more above adjacent floors or ground level to be a minimum of 42 inches high. As for the number of rails, a typical guardrail system may consist of a top rail, mid rail, and sometimes a bottom rail to prevent people from slipping underneath. The exact number of rails required can again vary based on the code or standard being applied.