its a rail, rails are made of metal, so are your skis edges. Metal on metal = damage
if you have ever done a rail at a resort then looked at your skis invision that look, its gona be the same. The only thing that recks them more is when you biff hard and the ski smash's into concrete. So either yous your old/rock skis or find a cheep set of used ones if your really really worried about damaging your skis.