In New York City every bit of space counts. The rear hall of this Upper West Side apartment was generous but underutilized. Custom built-ins transformed a hallway into an office that can be shut out of site when work is done or company comes. The cabinetry contains a drop-down desk, filing cabinets, storage for office and computer equipment, thin shelves for paperback books, and deep shelves for the display of art and objects brought back from the client’s trips abroad.