Editing Cross-country skiing (section)

====Traction surface====
{{main article|Ski wax#Grip wax}}
Skis designed for classic technique, both in track and in virgin snow, rely on a traction zone, called the "grip zone" or "kick zone", underfoot. This comes either from a) ''texture'', such as "[[fish scale]]s" or [[mohair]] skins,<ref>{{Cite web|last=Jhung|first=Lisa|date=2020-12-05|title=This Is the Winter to Invest in Cross-Country Skis|url=https://www.outsideonline.com/2419169/how-buy-cross-country-skis|access-date=2021-03-02|website=Outside Online|language=en}}</ref> designed to slide forward but not backwards, that is built into the grip zone of waxless skis, or from applied devices, e.g. [[Ski skins|climbing skins]], or b) from ''grip waxes''. [[Ski wax#Grip wax|Grip waxes]] are classified according to their hardness: harder waxes are for colder and newer snow. An incorrect choice of grip wax for the snow conditions encountered may cause ski slippage (wax too hard for the conditions) or snow sticking to the grip zone (wax too soft for the conditions).<ref name="Rees"/> Grip waxes generate grip by interacting with snow crystals, which vary with temperature, age and compaction.<ref name="Rees"/> Hard grip waxes do not work well for snow which has metamorphosed to having coarse grains, whether icy or wet. In these conditions, skiers opt for a stickier substance, called ''klister''.<ref name="Rees"/>