a wooden clapper is used to?

It's used for many things. Here's a start.

http://www.google.com/#sclient=psy&hl=en&q=wooden+clapper&aq=f&aqi=g1g-m1g-v2g-o1&aql=&oq=&pbx=1&fp=2d73bcec2e6e3c54

Btw -- if you'd have put your school subject in the subject line, I'd have been able to give you a more precise answer.