Security chains are physical devices used to secure items, such as bicycles, gates, or storage units. They are typically made of strong metal links that are resistant to cutting and tampering. Security chains often come with a lock, allowing users to fasten the chain around an object and secure it to a fixed point, providing an added layer of protection against theft. These chains vary in thickness, length, and material, with some designed for heavy-duty use while others are more lightweight for convenience. When choosing a security chain, it's important to consider factors like the level of security needed and the specific application, ensuring that it meets the requirements for protecting valuable items.