These are skis for skating on snow. Skis are a device consisting of two long boards with an upward curved front that are attached to the legs. Skis are usually made of wood or plastic. Almost all the varieties of skis that are produced from 2000 to today are constructed according to a new technology, which is characterized by a parabolic structure of the ski. With the old technologies, the two sides of the skate are parallel lines. In contrast, the two sides of the new skis are mirror parabolas. The top part of the skirt is wide, the middle part of the skirt is narrower and the back part of the skirt is wide. For different types of skis, the ratio of upper, middle, lower part may differ. Although it is not clear who invented the ski, the oldest skis were wooden and were found in Russia. The first skis were not used for leisure, transportation or to achieve higher speeds. Their main purpose was to keep people on the snow while hunting. Early skis were usually accompanied by poles to help maintain balance.