Connection points can be placed anywhere on most nodes. Each connection point defines a location in addition to the center point where a path can be attached. When attaching a path to a node, the endpoint snaps to the nearest connection point, or automatically creates a new one if you choose.
Connection points

Connection points do not normally print with the diagram, but you can choose to have them marked as black dots if required.

There are a number of convenient methods for adding connection points to a symbol: