A set of press-fit building blocks for making human-scale items like furniture, desks and shelving. This set is more about framing where voids (walls and shelves) can be filled with solid faces made from any material (like laser-cut wood & plastics). Specialized shelving bars make this easy.
These require a minimum of two shells (three is better) and 15-20% infill. MakerWare's honeycomb infill is the strongest in my experience. Hatchbox silver PLA (on Amazon) looks a bit like brushed metal when printed vertically as long bars.