Sleet is the hardest kind of night — heavier than snow, meaner underfoot — and it arrives in the small hours over the Roxbury streets near Scalzi Park with a sound like sand thrown at the windows. Galletta Bros Services runs snow removal through weather like that, working driveway after driveway with the plow and finishing walks, steps and entries by shovel. Ice control goes down where the drive meets the road, the spot that catches everybody. If a storm doubles back, so do the trucks. The measure of the job is simple: the car goes out, the mail carrier gets up the path, and nobody slips.