Toward evening the Ayer Road corridor at the edge of Harvard empties out, and what is left is pavement, curb islands and grass strips that either look cared for or plainly do not. Landmark Maintenance & Construction works that difference. In the green months it is mowing, trimming, edging and cleanups on both house lots and business properties; in winter it is plowing lots and drives, clearing entrances and walks, and sanding the spots that freeze first because they always freeze first. Sitting between Devens and the back roads, this stretch of town sees both kinds of ground in a single day, tight commercial aprons and long rural driveways. Opening a lot before the first car turns in is not glamorous, but it is the reason a place can run at all.