Bay State Exteriors keeps to the rooflines of Salem, New Hampshire — that pocket of Rockingham County where the Spicket River threads past Canobie Lake and the Massachusetts line sits close enough to feel like the next street over. Their trade is the outer shell of a house: asphalt and rubber roofs, repairs and inspections, vinyl and cedar-impression siding, gutters and downspouts, replacement windows and doors, and the deep-February work of clearing ice dams off the eaves before the melt finds its way indoors. There is a plain satisfaction in that kind of labor — a course of shingles laid straight as a hemlock's shadow, a downspout running clear, a roof that gives winter nothing to hold onto. They carry it south through Windham, Derry, Pelham and Plaistow, over the border into the Merrimack Valley and out along the North Shore, and indoors as well, where kitchens, baths and accessory dwelling units get the same steady attention. When the thaw finally comes off a house they have tended, it goes exactly where it should: down the spout, into the yard, gone.