The Select menu > Select command brings up a submenu with three choices. Those choices are:
Pointer/Window: This command sets Section Designer in its default select mode where you can select shapes either by left clicking on them or windowing them. Anytime you are in select mode (not draw mode) this is the default mode of selection. Thus in most instances it is not necessary to click this command before making a selection. You can just simply make the selection by left clicking or windowing. The primary use for this command is to switch you out of draw mode into select mode.
Intersecting Line: This command sets Section Designer in the intersecting line select mode.
All: This command automatically selects all shapes in the section.