A forcing bag — more commonly called a piping bag — is a cone of fabric, plastic, or disposable film fitted with interchangeable nozzles, used to squeeze soft foods out in controlled, decorative shapes. Pastry chefs fill it with icing, cream, choux paste, meringue, or puréed potato and pipe borders, rosettes, lettering, and uniform portions with precision no spoon can match. Nozzle shapes determine the effect: star tips give ridged shells, plain tips give smooth lines and dots. Disposable bags dominate professional kitchens for hygiene, while reusable cloth bags suit home use. Skill with the bag — steady pressure, consistent angle, clean cutoff — is a foundation technique of patisserie and cake decorating.