What is the difference between a kerb trim and an arris rail?
An arris rail is a 45 degree bit of timber that was commonly used on felt roofing. With EPDM rubber roofing it's easier to allow the EPDM to come over the edge of the roof and then use a kerb trim that prevents water flowing off that edge. Kerb trims are also known as a raised edge trim on GRP & Liquid roofing.