Containers are symbols that surround and enclose other symbols to show groupings or divisions within a diagram. Special properties make containers suited to this purpose. Containers are transparent so that other symbols are never hidden when inside their bounds. Containers are also created with a different procedure that allows you to immediately define the bounding rectangle rather than stamping out a fixed sized shape.

A container symbol can also be designated as active. An active container forms an informal group among the diagram elements it encloses. Its contents move when the container is moved. They are copied when the container is copied, and they are deleted when the container is deleted. An active container acts like an ad hoc group. But an active container is more convenient than a true group because you can manipulate its contents without ungrouping and regrouping.