If you want to use a line to connect shapes and keep them connected, you may want to draw a connector instead of a normal line. A connector looks like a line, but it stays connected to the shapes you attach it to.
Do one of the following:
Draw a line
If you just want to draw a straight line, click Line on the Drawing toolbar, and then drag to draw the line.
Draw a connector
Connection sites appear as blue circles as you pass the pointer over a shape.
Locked or attached connectors appear as red circles. Unlocked connectors appear as green circles.