It should completely cover the backer rod with no visible gaps between the paver and sealant. Sprinkle sand gently over the sealant as it's drying. Read the original article on House Digest .

Steve’s dad told him backer rods are used in anything with expansion joints – high-rises, roads, ramps, runways – you peel away the caulk or tar and there’s a foam rod in there to seal it ...