This is a strong reason to be nostalgic of the past! According to Wikipedia, Vac-u-former was a toy made by Mattel in the 1960s. Based on the industrial process of vacuum forming, a square piece of plastic was clamped in a holder and heated over a metal plate. When the plastic was soft, the holder was swung to the other side, over a mold of the object to be formed. Then pressing a handle on the side of the unit created a vacuum, sucking the plastic down over the mold and shaping it to it. When the plastic cooled it solidified, making an impression of the item. Various molds came with the kit, but almost any small object could be used as a mold.