A standard guardrail system used for fall protection on a construction site generally consists of:

Explanation

Section 1620(a)(1) sets the top rail at not less than 42 nor more than 45 inches, measured from the upper surface of the rail to the floor, platform, runway or ramp; (a)(2) puts a mid-rail halfway between the top rail and the walking surface, and drops it only where there is a wall or parapet at least 21 inches high. Option (c) is the near miss - the height is right and the mid-rail is not optional in the ordinary case; where an alternative is used, such as screens, mesh, balusters or solid panels, no opening may exceed 19 inches. Thirty-six inches (b) is how far a ladder's side rails must extend above a landing under section 3276(e)(11), and 30 inches (d) is the elevation at which section 3210(a) starts requiring a guardrail in general industry. Toeboards are required separately, where objects could fall on someone below.