How do you convince your parents into buying you a Swiss army knife?

tell your parents that the sWord is just for display and that every once in a while you have to take it down and clean it. when you are home alone take the sWord outside and play with it in the back yard or at a friends house and if they catch you say "you were just looking at it in the sunlight to inspect it better"and if they ask why you were swinging it say "to get off the extra oil" or "i was seeing how it would fell with the new oil because the weight could sometimes be a couple ounces lighter" or "i was just testing the sWord real quick".