This is the G Scale Grid Shelving - 15 x 24 black from Aristo-Craft Trains.
Bring Large Scale Railroading into almost any room in your house with the new Transit System. Using familiar shelf brackets and specially designed shelving units, the system creates an attractive, modular support for your railroad. The basic support is the Straight Shelf, measuring 15" wide and 24" long. The brackets are secured to the interior studs in the walls, while the shelves and the tracks are secured with heavy-duty, locking cable ties. The see-through grid pattern provides an open look to the shelving so it blends with the room decor without becoming a dust collector. The shelves can also be covered with foam board for use with smaller scales, providing a light-weight, easy-to-build benchwork system.