Yesterday we were at Barnes & Noble, and I was flipping through the book LEGO Crazy Action Contraptions when I ran across a gragger. They call it an 'annoy-o-matic', and it is often called a 'ratchet instrument'. The reason to note it here is that this is part of a Jewish tradition at Purim. During the Purim celebration, the story of Esther is read. Whenever Haman is mentioned, everyone makes noise, often with graggers, to blot out his name forevermore. You may recall that I've previously blogged Joanna Brichetto's LEGO graggers. BTW, doing some online searching, I found a similar Easter tradition in some parts of the Czech republic, where the noise is to chase away Judas.
Joanna gives instructions for her graggers. If you look at this version from the Crazy Action Contraptions book, it's fairly similar to hers and pretty easy to make.