Remove the snow plow from the ATV mounting frame. It will be much easier to sharpen the plow with it set at a convenient height in which to operate the grinder.
Place the snow plow on a work bench or a set of work horses with the plow edge facing up and towards you.
Use those safety glasses and place them over your eyes. Whenever you operate a grinder, metal pieces will become airborne and could lodge into your eyeball, causing a serious injury.
Plug the grinder into the wall outlet and start the electric grinder.
Move the grinder parallel to the edge and lightly touch the revolving stone to the metal. Use the grinder in light, single passes removing any burred edges.
Run the grinder from one end of the snow plow edge to the other end. It is better to take multiple light passes with the grinder than one heavy pass.
Check the straightness of the grinder work by stopping the grinder and laying the straight edge ruler against the snow plow. The two edges should mate evenly along the length of the blade.
Use the black dry marker to identify any trouble spots along the metal edge. Mark the blade in black lines and then use the grinder to "dress out" any deep burrs or raised metal parts of the blade.
Repeat Step 6 through 8 until the edge of the snow plow is mated completely to the straight edge ruler.
Reattach the snow plow to the ATV and test the blade for debris removal.