In Romeo and Juliet, Gregory and Sampson walk a very fine line when it comes to stiring things up. In Verona it is considered to be a rude gesture to bite one's thumb and flip it. They start to do so, but make it look as if they are truly biting their thumbs (but not flipping) so that they could 'technically' say that they never offered insult and it was the other parties that started the fight. In other words, they are all talk, but no true action.
