Final answer:
When working at heights exceeding six feet, it is a safety requirement to use guardrails, mid-rails, and toe-boards according to OSHA standards.
Step-by-step explanation:
The question pertains to workplace safety requirements, specifically when working at heights. In the context of such safety measures, OSHA (Occupational Safety and Health Administration) standards typically require that if working at a height of more than six feet in the construction industry, appropriate fall protection such as guardrails, mid-rails, and toe-boards must be used. These systems are vital to prevent workers from falling off an elevated work station, which could result in serious injuries or fatalities.