Connecting links are also known as master links. They're used to join the ends of a chain length. The side plate is easy to remove for attaching to a chain. Adding links are also known as roller links. They require two connecting links to join chain. Adding-and-connecting links are also known as half links and offset links. A combination of connecting and adding links, they join chain that requires an odd number of links. For trade number 35 and up, the side plate is easy to remove for attaching them to chain.