To limit the probability that the flow of water down a roof's surface will be interrupted by a wide chimney, which could lead to a temporary increase in water depth beyond the depth protected by roofing or by the vertical leg of flashing at the chimney, which could lead to precipitation or meltwater ingress, which could lead to deterioration, which could lead to the structural failure of roofs or chimneys, or elements protected by such assemblies, which could lead to harm to persons.