If you do not select any items in the WBS list, the user will have access to all elements.
Items preceded by a 
sign can be expanded by clicking on the 
sign.
Items preceded by a 
sign can be collapsed by clicking on the 
sign.
Only items with check marks are selected.
If a collapsed item is selected, its children are included in the selection.
If an expanded item is selected, its children are not automatically included. They must be selected individually.