Cross terrains have far more sidecut than the usual run of steel-edged waxless BC skis; 1 degree base bevel and 1 degree side bevel so you're not constantly hooking the little toe edge when climbing across the hill and to mimic Y2K-era SL ski edge engagement when making turns. Alpinord mentions a flat-plate faced guide (instead of one with wheels, for example), and I would agree. It won't be reliable for accurate geometry on the scaled portion, and you will only be able to use it tip-to-tail, but it's better than nothing.
Since the bases are scaled, it sounds like you have the recent (2010 and later- orange?) Cross Terrains.
I assume you know to use spray-on glide wax on the scale portion and to brush it out with your nylon brush.