SRC EnduraLine Permanent Warning Line System. The EnduraLine Warning Line system is our most robust warning line system we offer. Most commonly used for permanent demarcation on roofs and placed 15 feet in from the roof edge. This type of installation allows coverage of large open areas of roof economically and in areas where there is serviceable equipment within 15 feet of the roof edge, the SRC 360 Mobile Railing System is utilized. This combination of protection systems affords 100% perimeter protection for personnel on the roof. This visual warning line system utilizes heavy-duty cast iron plates, stainless steel cable and aluminum pennants all designed to last for years in the most rugged outdoor environments. Available in powder coated colors or galvanized finish.