In glaciated terrain the risk of crevasses means that even technically easy walks require the use of rope, crampons and ice axes as well as knowledge of safety and rescue techniques. Techniques and equipment, the use of which can become especially important in high mountain tours, include crevasse rescue, the T anchor, the ice screw and snow protection. Walking with a rope requires a roped team to be formed and makes trekking alone dangerous. In addition, a certain level of fitness and height acclimatization is often unavoidable. Especially for mountain tours in high mountains such as the Himalayas, the Karakorum or the Andes, which reach elevations of over 6,000 metres above sea level, one or two weeks should be allowed for acclimatization. Low temperatures may also be an important factor.