Climbing skins are an innovation for cross country skiers that allow them to perform climbs with much less effort than was previously required. The first skins were quite literally a seal’s skin, which was put on the underside of skis. The premise behind a skin is that a ski needs to be able to move forward, but not slide backwards. A seal’s pelt provided the first natural solution to this issue, because the patterning of the hair allowed a seal to move dynamically through the water forwards, but it also prevented the water from penetrating to the seal’s skin with layering.
The action of the seal’s hair in the first climbing skins has since been mimicked in synthetic (and animal free) ways. A modern ski skin can be put on while ascending and removed for descent, which greatly adds to the versatility of any skis. Instead of packing your skis up the ridge and tiring yourself out before you even get to the run, you can wear the skis and make them help your way up the slopes instead of hurt them.
Whether or not you use climbing skins however, it is vital that you understand and are competent in handling the dangers of back country skiing. The first mistake you can make is to assume that you’re only in avalanche danger when making your run. Choosing the proper ascent line is as important (some would say more important) as your line of descent.