There's a point to this superstition
Very superstitious people consider giving a knife -- or anything sharp for that matter -- as a gift to be bad luck. Some say the knife will cut the friendship or hurt the other person. To prevent this, the recipient must "buy" the knife from the gift giver -- and a penny will do. Some people simply tape a penny to a knife. The French give a knife with a penny attached to chefs so they won't hurt themselves and cut short a career (couper le metier). -- SHERYL JULIAN 