A standard rail shall consist of top rail, intermediate rail, and posts, and shall have a vertical height of?

• A. 36 inches
• B. 60 inches
• C. 48 inches
• D. 42 inches

Answer: (D)

Guardrails are designed to prevent falls from elevated work areas, and a standard three-rail system uses a top rail, an intermediate rail, and posts to form the barrier. The top rail is placed at a height of 42 inches above the walking surface, with the intermediate rail positioned below it. This height is chosen to provide effective fall protection for most adults while keeping the barrier practical to work around and operate near. OSHA and similar safety standards specify this 42-inch height as the typical minimum for guardrails in general-use applications, with some tolerance around it.

So, 42 inches is the standard vertical height because it balance-protects workers without being overly restrictive or hard to use. The other options fall outside the commonly required height for standard guardrails.