Holmenkol Crossfile Maxi 

"The Crossfile Maxi from Holmenkol is a world cup proven, coarse file that has been specially developed for pre-grinding ski and snowboard edges. It offers outstanding performance that even meets the requirements of professional athletes. Perfectly suited for skiers who want to optimally prepare their equipment to achieve top performances on the slopes."
"With the Crossfile Maxi you can pre-grind the edges of your skis and snowboards with precision and efficiency. The robust design and the large file surfaces guarantee a long service life and consistent grinding performance. This is the ideal tool for anyone who values perfectly prepared edges and relies on proven quality."