More often than not, rigged gambling involves games of chance such as the shell game. In Egyptian times, it was called the cups and balls game, and in the shell game actually dates back to ancient Greece.
A shell game is known as a short-con, simply because it is a quick and easy way to make money. It does not require an intricate setup and the operator (shell man or thimblerigger) only needs three shells and a small ball or pea, a sidewalk or cardboard box.
The essence of the game is the pea is under one of the shells and after being quickly shuffled by the operator, the mark is to guess which shell the pea is under – after placing a hefty bet. The confidence trick is that typically the pea or small ball in not under any of the shells, as the operator has palmed it. Thus, it is almost impossible for anyone to win a shell game, unless the person running it allows that to happen to suck the mark in further.
The other aspect of this type of gaming is the small crowd surrounding the shell man. They are not playing, they are there as muscle and police lookouts, and to keep a hooked player in line and ignorant about how the game is actually run.