Almost idiot proof. I'd cut BD skins before and there was the effort to set the skin slightly offset each side to trim the right amount off. With the G3 tool you simply put the skins on the center of the ski and run it down the edges. It's set to cut the appropriate distance in to clear the edges.

This thing is a cinch to use. Buy a couple (like your shaver, it dulls slightly with each use) and have your buddies pay you to cut their skins. Perfect results with no practice. It's sized to leave your base edge plus just a few millimeters of ptex showing so edging and side-hilling are no problem-o. Mine came with my G3 Alpinist skins. I used it to cut mine and then cleaned up my roomies BD Ascensions. Still sharp enough for another job, but I'm looking to grab another just to be on the safe side.