many types of skis have been developed, designed for different needs, of which the following is a selection. Alpine Alpine skis, also called downhill skis, are skis designed specifically for lift-assisted resort runs. Ski design has evolved enormously since the beginnings of the modern sport in mid-19th-century Norway. Modern skis typically have steel edges, camber, side cut, and possibly reverse camber. During the 1990s side cut became more pronounced to make it easier to carve turns. Alpine skis typically have fixed-heel bindings. Specialised types of alpine skis exist for certain uses, including twin-tip skis for freestyle skiing, slalom skis, GS Skis, powder skis, telemark skis and monoskis. Backcountry Backcountry skiing, also known as off-piste skiing, is any form of skiing done outside of ski area boundaries. Most of the time this type of skiing is done with alpine touring skis, or telemark gear, where skiers take advantage of climbing skins and a detachable heal, to ski uphill. When the skier reaches the top of the area they want to ski down, they take off the climbing skins and make the necessary preparations to ski back down. Backcountry terrain can also be accessed with standard alpine equipment by riding a lift uphill at a ski resort and then leaving the resort boundary. However, this is more commonly known as sidecountry because of its immediate access from a ski lift. Nordic In Nordic skiing the skier is not reliant on ski lifts to get up hills, and so skis and boots tend to be lighter, with a free heel to facilitate walking. Styles of Nordic skiing equipment include: Cross-country skis are light and narrow, with a slight sidecut. Three binding systems are popular: Rottefella's NNN, Salomon's SNS profil, and SNS pilot. Ski bases are waxed to reduce friction during forward motion, and kick wax can also be applied for grip. Some waxless models have patterns on the bottom to avoid the necessity of grip waxing for classic technique. Skating skis are shorter than classic skis and do not need grip wax. The skating technique is used in biathlons. Ski jumping skis are long and wide. Roller skis have wheels for use on dry pavement, in the absence of snow. Ski Maintenance Ski maintenance encompasses four facets: binding adjustments, waxing, edge shaping, and base repair. Binding adjustment: Safety-release ski bindings require adjustment to fit the weight and height of the skier. Annual maintenance