A Saturday in July around here sounds like sprinklers, a ballgame carrying over from Butler Park, and mowers starting up one after another down the block. Lawn Teens is part of that sound — cutting, trimming and edging yard by yard through the long bright middle of the year. Grass comes down evenly, walks and drives get an edge, and clippings get cleared instead of left in gray windrows across the turf. Cleanups in spring and fall round out the calendar, when the beds need opening and the leaves need moving before they mat. There is something plainly good about handing a yard back at noon, cut and swept, with the whole weekend still in front of it.