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.