The Jack Knife

In a momentary lapse of judgement I bought Jack a used pocket knife for $1.  He asks to use it all the time.  I allow him to cut the branches of our hedge with it, so that the overgrown beast gets trimmed a little at a time.  I supervise him and albeit sometimes from the window, and told him some rules about using a knife.  So far he has only chased Gracie with it once and then he lost it for awhile as a result.  Now when he wants to use it. he asks, "Mom, can you supervision me?"