To limit the probability that shingles will not form a continuous waterproof membrane, which could lead to rain or meltwater ponding on low-slope roofs and penetrating past shingles under wind-uplift or hydrostatic pressure, or capillary action, which could lead to water penetrating directly to roof decking or sheathing, which could lead to deterioration, which could lead to the structural failure of roofs or assemblies protected by roofs, which could lead to harm to persons.