[Acorn]

Tdrcreyn4's method is the best. But if you don't have the fancy tools you could try my redneck method. Trace the templet, then use what ever size drill bit you have and drill holes all along the inside perimeter of your templet, then use some good sharp tin snips and cut it out. Then file off any sharp edges. It's hard to make it look 'factory' this way but you can't tell once you put the vents on.