Clackers were also known as Klik-Klaks, Whackers, Bangers and Knockers. They consisted of two hard plastic balls each linked to a ring with a piece of string. The aim was to swing them so they hit each other and made a noise. They caused a number of injuries and were banned in many schools. The craze was short-lived but they have made a comeback in recent years. They now have a plastic handle join instead of the strings and are much safer.