Which component is used to connect two or more lengths of chain securely?

In the context of connecting two or more lengths of chain securely, a shackle is specifically designed for this purpose. Shackles are typically metal fastening devices that feature a U-shaped body and a pin or bolt to secure the connection. They are widely used in rigging, lifting, and towing applications because they provide a strong and reliable link that can be easily opened and closed, allowing for quick modifications and adjustments without compromising the integrity of the connection.

While other options such as connector links and carabiners serve specific functions in joining chains or ropes, they are not as robust or commonly employed in heavy-duty applications as shackles. Connectors and link pins might be used in lighter applications or different contexts, but for securing heavy chain lengths in industrial or construction settings, a shackle is the most appropriate and reliable choice.