The Old Croton Aqueduct runs under a green ribbon of grass straight through Yonkers — turf laid over buried stone, and in May it is the brightest thing in the city. Straight lines happen to be the business. Gonzalez & Sons Landscaping Inc mows, trims and edges lawns, shapes beds and keeps the borders honest where grass meets walk, driveway and fence. Turf will claim a foot of pavement in a season if nobody stops it. Kept in its lane, it makes everything around it look sharper, which is the quiet argument for a good edge.