A material, such as minimum nominal #1-1/2 inch size or #4, or alternatively, #3, #24, #2 or #1Ñas specified in ASTM D448Ñsmooth river stone, crushed stone, standard precast concrete pavers or interlocking, beveled, doweled or contoured fit lightweight concrete pavers, that employs its mass and the force of gravity to hold a roof membrane system in place.

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