To Join Two Chains
You can join chains created at different times, or broken by deleting points in the middle of them.
1. Place the cursor on an endpoint of a chain and press 0. The point highlights and you are prompted to select another chain endpoint. To abort joining the chains, press 3.
2. Move the cursor to an endpoint of the other chain. Press 0. The two chains become one with a new line segment between the two selected endpoints.