Posted By Martyn Hendrie Have you looked at HSE publication HS(G) 33 Health and Safety in Roofwork? [ISBN 0-71-761-425-5] In my experience "North Lights" should be treated as if they were an open edge and be suitably protected. Usually by placing suitable plywood sheets or similar along the work area and access route. However, care needs to be taken to secure the sheets from being blown about, or from, the roof creating another risk