The knob you turn on a deadbolt to open the door keeps falling off. There is a small screw at the bottom of it. My lock kit came with an allen wrench that I think fixes it, but it got tossed in the shuffle. Does anyone know the standard size of this tiny allen wrench? I went to Home Depot and bought an assortment of sizes but the smallest size is at least 1 size too big. I found I could kind of turn it a little with the blade of a pocket knife I have. It is still falling off though. I don't want to call a locksmith. I would prefer not to commit fraud by buying the lock kit I have, using the tool, and returning it. Any ideas?