Thread ball is a type of craft that involves winding yarn or thread around a core material to create a decorative ball. It is a popular craft for children and adults alike, as it is easy to do and requires minimal materials. The term 'clew' is used to describe the core material used in thread ball, which can be anything from a Styrofoam ball to a balloon. Thread ball is a great way to use up leftover yarn or thread, and can be used to make decorations, toys, or even jewelry.