Greetings from Vermont, Welcome to the Club!
the Tool?, When field dressing a deer, cutting out the anal cavity can be kind of messy exposing the meat to unwanted bacteria,
the tool is supposed to make that part of the process a little cleaner and reduce the bacteria risks.
Personally I dont use it because I've done it enough to make sure I dont make messes. Now I probably just jinxed myself...
Anyway, Good luck and Happy safe hunting always.