These little pieces were designed to slot together to build a complete model car, boat or glider included in a series of books. The models were printed on rectangles of card, and dropped into a pocket attached to the side of each double-page spread. The illustrations were required to be as accurate as possible, bearing in mind the jigsaw-like quality of the concept. The planes fly, the boats float and the cars park. Later series included the model diggers, robots and an anatomical human figure, which plays "Santa Claus is coming to town".