Trace a drawing of a knife onto a piece of cardboard. Cut out the cardboard knife shape.
Trace the handle of the knife onto another piece of cardboard, and cut it out. Repeat until you have four cardboard handles, the exact shape and size as the handle of the cardboard knife.
Coat the cardboard knife with glue and completely cover it with aluminum foil. Allow it to dry.
Glue two cardboard handles onto one handle side of the cardboard knife, and the other two pieces onto the other side of the handle. The blade will be sandwiched between the cardboard handles.
Wrap black electrical tape around the handle of the knife and cover it completely.