Memory foam is dense foam that can mold to the shape of the body. Memory foam is frequently used in pillows, mattresses, mattress toppers and cushions. According to the Memory Foam Reviews site, 4-inch memory foam is suitable as a topper for a mattress. With a few simple tools, 4-inch memory foam can be cut into various shapes and sizes.
Measure the foam and trace the desired size and shape with a pencil directly on the memory foam.
Lay the memory foam on a surface that is safe for cutting.
Cut the memory foam with a serrated electric knife. Press the electric knife gently against the memory foam when cutting. Forcing the knife through the foam can result in rough edges. Hold the knife straight. Do not cut at an angle unless angled edges are your desired result.