Someone was talking about skinning up to UBSL on the WPSMB. I know this is probably a dumb question but what is skinning? Is it a form of snow shoeing?
Rod, look at the picture in Mike's Wikipedia link in the techniques section. Skins were originally made of seal skin, but now are simply a fabric with the nap set such that the skis will slide forward, but not backwards. The skins usually loop over the tip of the ski, and have a very sticky adhesive surface so they adhere to the bottom surface of the skis.
Skins work better than the fish scale pattern imprinted on the bottom of x-c skis, so people can go up steeper slopes. But they still have their limits. At that point, people would need to resort to snow shoes or crampons.
Of course, in some conditions, you just become part of the "snow relocation team"... You think skis are heavy by themselves, try adding 10 pounds of balled up snow...