In my previous post regarding using the marking pen, I failed to mention that I was assuming that the base is flat and the base edge is flat and flush with the base. This isn't always the case. Sometimes I don't want to take the time to flatten the base and base edge, and I don't want to remove that much material. A lot of skis are a little bit concave in the wider areas near the tip and tail, and the use of a file guide which slides along the base will result in an inaccurate bevel. If they ski OK the way they are, and all I really want is a sharper edge, what I do is try to follow the existing factory edge bevel with a diamond file without using a file guide. If I do enough filing on the base edge, I eventually cut into the base which I then have to flatten a little. For that purpose I alternately use a steel scraper and a Skivisions base flattening tool with a stone blade to cut down the base a little so that it is flush with the steel edge. Frequent checking with a true bar helps make sure I don't make the base convex or more concave in the process.