A ski jumping hill is a sports venue used for ski jumping. They vary in size from temporary handmade snow structures to permanent competition venues. At the top is an in-run where the jumper runs down to generate sufficient speed, before reaching the jump. The skier is then airborne until landing on the landing slope. The last part of the hill is the out-run, which may be either flat or even uphill, allowing the jumper to stop. The steepest point of the hill is the construction point, which is used to determine the score of a particular length. The size of a hill is measured in the hill size. Hills with a hill size exceeding HS185 are designated ski flying hills; there are five such hills in the world.