The Rectangle At Bounds operation creates a rectangular path around the orthogonally-aligned bounds of each selected art object. The operation honors the general Illustrator preference Use Preview Bounds. Groups are treated as a single object unless Shift is held down when the button is clicked.
QuickOps Rectangle at Bounds
Clicking the icon to the right of the button will bring up the Rectangle At Bounds Preferences dialog:
QuickOps Rectangle at Bounds Preferences
Specifies the color of the rectangles. Clicking the color chip brings up the standard color picker dialog. The default color is black.
Specifies the stroke weight of the rectangles. The default weight is 1 pt.
Specifies whether the bounds rectangles are created above the original art, below the original art, or to replace the original art.
When enabled, the original art stays selected; otherwise the bounds rectangles become the new selection.
When Shift is used to create multiple bounds rectangles for each member of a group, these rectangles are also placed in a group when this preference is enabled.