Provided herein is an article of manufacture that includes a stop member having an upper surface and a lower surface, a blade extending upwardly from the upper surface of the stop member, and a handle attachment member extending downwardly from the lower surface of the stop member. The blade includes two sharp edges each having first and second ends and two blunt edges each having first and second ends. The first ends of the sharp edges meet at a point and extend away from the point at an angle of 90.degree. or less, and the first ends of the two blunt edges extend downwardly from the second ends of the two sharp edges. The angle formed between the corresponding sharp edges and blunt edges is obtuse, and the second ends of the two blunt edges are connected to the stop member.