Planes come in low over Norwood Park on the O'Hare approach, one every couple of minutes, and a July afternoon here gets measured in them. Towers Lawn Service works underneath that traffic — mowing the small square front lawns and the deeper yards behind, edging tight to the walk, trimming the fence lines a mower cannot reach. Clippings are cleared off the drive so the pavement ends up cleaner than it started. Weeding, mulch and a summer feeding keep the beds from going ragged in the heat. The engines fade, the mower cuts out, and the block is quiet and cut.