There is a lot of snow in the Northeast in winter. In Heilongjiang, it usually starts snowing in October (public), and it occasionally snows in May. In the open grasslands and forests, the snow is sometimes more than one meter thick. People will not sink into it when walking on it because the snow has been frozen and hard, and the snow on the road is firmly stuck to the road surface. At this time, a means of transportation called a sled is very useful, which can be pulled almost effortlessly. So it must be faster than a horse-drawn carriage. There are two iron or wooden slides at the bottom of the sled, which are used to contact the snow surface, and a horse is pulling it in front. The horse's hooves must also be iron-shod so that they don't slip on the road.