molding machine in 1947. One of the first modular toys to be produced was a truck that could be taken apart and re-assembled. In 1947, Ole Kirk and Godtfred obtained samples of interlocking plastic bricks produced by the company Kiddicraft. Hilary Fisher Page designed these "Kiddicraft Self-Locking Building Bricks." In 1939, Page had applied for a patent on hollow plastic cubes with four studs on top (British Patent Nº.529,580) that allowed their positioning atop one another without lateral movement. In 1944, Page applied an "Improvement to Toy Building Blocks" as an addition to the previous patent, in which he describes a building system based on rectangular hollow blocks with 2X4 studs on top enabling the construction of walls with staggered rows and window openings. The addition was granted in 1947 as British Patent Nº 587,206. In 1949, the Lego Group began producing similar bricks, calling them "Automatic Binding Bricks." Lego bricks, then manufactured from cellulose acetate, were developed in the spirit of traditional wooden blocks that could be stacked upon one another but could be "locked" together. They had several round "studs" on top, and a hollow rectangular bottom. They would stick together, but not so tightly that they could not be pulled apart. In 1953, the bricks were given a new name: Lego Mursten, or "Lego Bricks." Plastic products initially were not well received by customers, who preferred wooden or metal toys. Many of Lego's shipments were returned, following poor sales. In 1954, Godtfred Christiansen had become the junior managing director of the Lego Group. His conversation with an overseas buyer struck the idea of a toy "system," with many toys in a line of related products. He evaluated their available products, and saw the plastic bricks as the best candidate for such a system. In 1955, Lego released the "Town Plan" as such a system, using the building bricks. The building bricks were moderately received but had some problems from a technical standpoint: their "locking" ability was limited, and they were not versatile. In 1958 the bricks were improved with hollow tubes in the underside of the brick. This change added support in the base, enabling much better locking ability and enhanced versatility. The company patented the new design, as well as several similar designs to avoid competition. Ole Kirk Christiansen died that same year, and Godtfred inherited the leadership of the company. Change to plastic bricks (1960–1969)