As far as I know six of the best is a British phrase that means six firm strokes of the cane. It might have originated in the boarding schools that we have all read about, where headmasters, and sixth forms and other terms not familiar to American ear are common.
Wherever you live, there is no one implement that feared more by most and loved by so few, as is the cane. I view it as the most exquisite of all implements. It takes skill to use. When done right the effect is to be treasured.
Here are six of the best of my collection of caning pictures collected over the years from the web. I don't recall ever having one taken while I was using the cane. A pity as I am not likely to use one again.
I always retain watermarks, so if you are the owner of any these not marked, I will gladly remove or credit them as you may direct.