Cross country skiing has two basic propulsion techniques, which apply to different surfaces: classic (undisturbed snow and tracked snow) and skate skiing (firm, smooth snow surfaces). The classic technique relies on a wax or texture on the ski bottom under the foot for traction on the snow to allow the skier to slide the other ski forward in virgin or tracked snow. With the skate skiing technique a skier slides on alternating skis on a firm snow surface at an angle from each other in a manner similar to ice skating. Both techniques employ poles with baskets that allow the arms to participate in the propulsion. Specialized equipment is adapted to each technique and each type of terrain.A variety of turns are used, when descending.Both poles can be used simultaneously (double poling), or alternating, in classic the alternating technique is most common (the diagonal stride) while in the skating technique double poles are more common.