With repeated use, a bamboo whisk, or chasen, will naturally lose its curved shape. The bamboo whisk heeper is used to return the chasen to its original curved shape. Your chasen will last longer too... by two or three times its natural life-span!
Tip: It also prevents deterioration if you immerse the chasen in warm water before using it. This softens the bamboo, making it less brittle, so there is less chance of breakage.