The information below is intended only as an overview of base structuring. To learn more about the process, check with a qualified REI Ski Shop employee.
Step 1: Leveling—Ski bases glide most efficiently when they're perfectly flat. Subtle high and low spots can develop as a result of wear, age or the grinding and sanding processes used to produce the ski bases in the first place. Experienced skiers typically check their ski bases when they first buy them and at least once a season to make sure that they are still level, or "true." Leveling involves:
Identifying high and low spots using a "truing bar" or reliable straight edge.
Scraping or sanding down high spots and filling in low ones (with a P-Tex repair candle).
Finishing repairs by wiping and smoothing the base surface with a fiber pad or a wiping tissue (before waxing).
Step 2: Structuring—Imagine 2 wet panes of glass that have been pressed together. The same type of suction that makes these panes difficult to pull apart can develop between ski bases and the snow they slide across, if those bases are absolutely smooth.
When performed correctly, base structuring improves the glide performance of certain types of cross-country skis by eliminating this type of suction. Structuring involves carving thin, shallow grooves ("rills") into the smooth surfaces of your ski bases before you wax, so that melt water under your skis (formed by the friction between your skis and the snow) has channels to escape through.
Proper rills run the length of your skis and vary in size depending on ski conditions: wider when conditions are warm and the moisture content of the snow is high, narrower when conditions are cold and the moisture content is low.
NOTE: Typically, only skilled skiers and racers perform base structuring. Don't attempt to structure your own bases until you've received proper training from an experienced technician. Structuring is not recommended for skis with extruded P-Tex bases; nor should it be done across built-in grip patterns.