A June morning in Chester Heights smells like cut grass before it smells like anything else. Ambrose's Lawn Maintenance is part of the reason — mowing block by block, trimming close along the wrought-iron fences, edging the walk until the concrete shows a clean gray line again. Mount Vernon yards are compact and much loved, framed by hedge and brick and somebody's tomato plants, and they reward attention the way a small room does. Clippings leave with the crew; what stays behind is a lawn that looks glad to be looked at. By afternoon the light comes flat and gold down the side streets and the block reads finished.