A meat-fold is a communal activity. Basically, you gather all your meat slices (the kind that come in packets, such as turkey or honey ham) and lay them out on a picnic bench. I'd say the average packet contains about 20 slices, give or take. Then have everyone bring their garnishes--cheese, condiments, oils, pickles and the like.
The original idea of a meat-fold is that these garnishes can be distributed between some of the meat, and then the meat is folded over on itself, hiding what is (or isn't) inside. When garnishes are limited, some of the meat will not have anything in it. Other meat will have a nice dollop of mustard, or oil, or pepper or whatever else has been brought. The folds are handed out in equal ration, at random, to those participating.
The intent is that some will feel lucky when they get a fold filled with goodies on the inside. But, even in instances where your meat-fold is empty on the inside, you still don't feel too bad...even in the worst case, you're still getting some delicious meat!