A "screw-on" refers to a type of closure or attachment that is secured by twisting it onto a corresponding threaded surface. This mechanism is commonly found in various products, such as bottles, jars, and containers, where a tight seal is necessary to prevent leaks or contamination. The threads on both the cap and the container allow for easy opening and closing. Screw-on closures are often made from materials like plastic or metal, providing durability and convenience. They are widely used in everyday items, including screw-on bottle caps for beverages and screw-on lids for food storage, making them practical for both consumers and manufacturers.