a clamped straightedge and a router or a clamped straightedge and a jigsaw with a down cutting blade. we just redid our kitchen cabinets and i had my wife check the height of new fridges since i know ours wont last forever and the new ones were taller so i put a 12 inch cabinet instead of the 15 that was there and put a 3 inch filler under for future adjustments. the router would prob give you the best cut and they do make router bits that cut downward with a spiral cutting edge.