Another important characteristic of the structure chart is that the Z-Order also defines the "tab sequence" order for the objects. The tab sequence order is the sequence in which objects gain the input focus when the Tab (or Shift + Tab) key is pressed, and is important for users who prefer to use the keyboard rather than the mouse. For example, if a form consists of five frames, each of which contains a number of form fields, then for a keyboard user to get to some specific field inside one of the frames, it is best if the tab sequence order of the frame objects reflects their physical locations within the form. The structure chart thus provides a visual representation of the tab sequence order. Altering the tab sequence order is accomplished by moving the objects in the structure chart either up or down as required. The physical layout of the form or display does not change so long as no ownership changes are made: only sibling objects are moved up or down with respect to one another.