A piece of nonsense (proof) what if all you do is beat of trial spaniels or a boy that's working terriers, for all that is coming off a spaniel as a pup 1/2 a inch of the end leaves a tail that you can see.
A terrier, the width of your hand as a adult, not a dock up it's arse, 3/4 inch off the end leaves a good handle for a working dog.