The game is typically initiated with both the players uttering the rhyme "One, two, three, four, I declare a thumb war", passing their thumbs over each other in time with this rhyme. The rhyme is sometimes extended with "Five, six, seven, eight, try to keep your thumb straight." or "Five, six, seven, eight. This should be a piece of cake." A regional variation in Boston is “five, six, seven, eight, open up the battle gate.” In South America, the starting song is "ésta es la pulseada china", as in France, "un, deux, trois, bras de fer chinois" ("this is the Chinese arm wrestling"), with the same thumb dance as in English.

A game played by two players in which the thumbs are used to simulate fighting. The object of the game is to pin the opponent's thumb, often to a count of three.

The players face each other and each holds out their left hand or right hand in a "thumbs up", and they link hands such that each player's fingers curl around the other player's fingers. Players may not use any of the fingers except the thumb to pin down their opponent’s thumb.