A three-person crew is installing a 40-module array on a flat warehouse roof whose bare edges drop 6 m on all sides. Their route from the hoist to the array crosses three unguarded skylights, and the building's maintenance staff walk that route weekly without harness training. Which fall protection arrangement should be installed for this roof?

Perimeter guardrails and guards over every skylight provide passive protection at both principal fall hazards: the unprotected roof edges and the openings along the hoist-to-array route. Because maintenance staff use that route weekly and are not trained to use harness systems, protection should not depend on people selecting, fitting, or connecting personal equipment. Installing perimeter guardrails and rated skylight covers for the crew, then removing the covers when array work is complete, leaves the weekly maintenance route exposed; protection must remain in place for ongoing access. Adding a requirement for maintenance staff to use restraint systems after harness training relies on personal equipment when the guardrails and skylight covers can protect them passively; the arrangement that keeps both crews protected without harnesses is more direct. A warning line and safety monitor with skylight covers does not provide the same edge protection as perimeter guardrails for this installation scenario, leaving workers exposed to a six-metre fall. Exam caveat: warning-line systems have limited permitted uses and conditions, so do not assume they replace guardrails for every low-slope roof task. Practical check: verify that each skylight guard is secured against displacement and rated for foreseeable foot traffic, and that perimeter protection remains continuous at access points.