A muddler is a bartender's tool, used like a pestle to mash—or muddle—fruits, herbs and spices in the bottom of a glass to release their flavor. Cocktails that require the use of a muddler include: * Mojito, made with light rum * Caipirinha, made with cachaça * Caipiroska, made with vodka * Mint julep, made with Bourbon whiskey * Old fashioned, made with whiskey or brandy