How to de-tune a snowboard
Some boards come with factory de-tuned edges, what this means is that the contact points (shown) are dulled. This is done to prevent your board from catching an edge which will cause you to fall. You can tell if your board is detuned by running the back of your nail across the edge of the board. If you see any of your nail on the edge your edges need to b de-tuned.
How to detune your edges
You can pick up a metal file from your local hardware store. Take the file and run it a 45 degree angle repeatedly on the contact points of the board until the edges become dull.