An icing bag — the piping bag — is the cone of cloth, plastic, or disposable film fitted with a nozzle, used for piping soft foods in controlled shapes. Filled with royal icing, buttercream, choux paste, or mashed potato, it extrudes precise lines, rosettes, borders, and lettering under the pressure of the decorator’s hand. Interchangeable nozzles — rounds, stars, petals, leaves — form the decorator’s vocabulary; steady pressure and clean technique form the grammar. Reusable cloth bags suit the eco-conscious but demand thorough washing — dried icing harbours microbes — while disposables dominate professional kitchens for hygiene and convenience. It is among the oldest and simplest of precision tools, and still irreplaceable.