The split lock washer: It is designed to be used only once. Install, tighten and should you have to remove the nut at a future date, you should use a new split lock washer.
Here is what I do: I use the lock washer and then tighten the nut and then drill a hole through the bottom of the nut all the way through to the other side and insert a nail and bend the end so it can not come out. That way, it can not come unscrewed and
fall off.