thumbs up - Thumbs up is globally considered as a sign of approval, the best, agreeable, 'OK', etc. It is a very obvious hand language that is very appealing and encouraging to see without being vocal. Our thumb which is the strongest finger of the hand is considered by many as the leader or head among the 4 fingers. So if the thumb presided, it seems that the 4 agreed on it... that's why the 'thumbs up' sign symbolizes finality.