A canning ring, also known as a jar lid or sealing ring, is a metal band used in the process of home canning. It is designed to create an airtight seal on glass jars, ensuring that the contents remain preserved and safe for consumption. The canning ring is typically used in conjunction with a flat lid, which is placed on top of the jar before the ring is screwed down. When the jar is heated during the canning process, the contents expand, pushing air out and creating a vacuum seal as the jar cools. This seal prevents bacteria and other contaminants from entering the jar, allowing food items like fruits, vegetables, and sauces to be stored for long periods. Proper use of the canning ring is essential for successful preservation.