A glass rimmer is a handy device that can be used to add a frosting of salt, sugar, cocoa or any other fine powder around the rim of a glass, creating an attractive look for cocktails such as Margaritas and Bloody Marys.
Most designs consist of a sponge section that contains lime juice, lemon juice or even water, with another section containing the powder. To decorate a rim, simply push the rim of the glass onto the sponge, then into the powder.