Vario base bevelling file guide from Kunzmann.
Vario Base Bevelling Guide
The Kunzmann Vario Base Bevel Guide fits all 25mm wide files and abrasives and controls your base angle in 0.5 degree increments to a max of 3 degrees. The bearing guide gives consistent low drag filing, the wheels large width minimises pressure bruising to the base surface.
A controlled bevel along the base edge will allow the ski to be a little more forgiving of errors. For general use 0.5 or 1 degree is normal. A steeper angle might in some cases be a little harder to initiate and release the turn. Certain race disciplines will require the more extreme setups.
Snowboards can also benefit from some base bevel treatment. It really helps provide a more forgiving toe edge and grip along the heel edge.