Boxes of carefully detailed millwork play off each other to create subtle use patterns for the penthouse apartment. The residence is designed to expand to accommodate different numbers of users: it is a pied-à-terre for a traveling couple, a place to perhaps host guests when they are there, or the location for a large party on two floors. A millwork door in the hallway serves a double purpose to help choreograph these use patterns: it usually aligns with the hallway but opens perpendicularly to direct guests away from the private quarters to the roof terrace. A second similar door does the same thing and closes off the private bedroom from a guest room. The space is therefore adjustable and expandable according to the particular needs of the users. A reduced palette of waxed pale oak, gray terrazzo and deep blues and grays maintains a consistent contemporary character across the apartment even as the space expands and contracts.