Gypsy Necklace by Vernet

They display a beautiful poppit bead necklace and give it to the audience for perusal. Then ask everyone to name a number.

They pull the necklace apart revealing a long string of pearls and hand it to the viewer. Then ask him to pull the ends of the chain and the string will break at the exact number chosen.

You can repeat the effect with a different number.

With chain and instructions