A warning line system, used in some low-slope roofing work, functions to:

解析

A warning line is a visual boundary, not a barrier and not a system that catches anybody: it marks the area within which roofing work may proceed without conventional fall protection, and employees are instructed to stay inside it except where the work must be done at the edge. Option (b) credits it with strength it does not have - California's section 1730(b)(2)(B) asks only for a 500-pound tensile strength so the line does not part when brushed, and the line stands 34 to 45 inches above the roof, which is warning height rather than guardrail height. Option (c) borrows a steel erection term, where a controlled decking zone is bounded by control lines under a different standard. Option (d) turns the header rule in the same subsection into a storage instruction: headers of roofing material are laid parallel to the edges to warn, not to mark a laydown area.