Way back in August of 2006 Craig (with the very much missed Gomez assisting) was kind enough to run a "Blackjacks & Saps" class here in the Knoxville area for our little group. Paul and I had done some work using Boston Leather Juniors and Midgets iirc prior. But, again to the best of my memory, it was this type of tight arc close in or entangled use of the sap that Craig taught that really brought home the incredible utility of this tool in that kind of a situation. It was an enlightening class, but Craig's classes always are.
I have several saps and blackjacks, including some of the Foster Brothers excellent tools, but I particularly like carrying the Boston Leather Junior as it's grip profile seems to allow me to hang onto and control it better...and it's really inexpensive. And it rides well in my right hip pocket alongside my TQ.
FWIW they are legal to carry in TN with impact tool training credentialing.
Thanks for the excellent information in this thread and subforum.