If the aboveThis argument is omitted then the command raises window so that it is above all of its siblings in the stacking order (it will not be obscured by any siblings and will obscure any siblings that overlap it). If aboveThis is specified then it must be the path name of a window that is either a sibling of window or the descendant of a sibling of window. In this case the raise command will insert window into the stacking order just above aboveThis (or the ancestor of aboveThis that is a sibling of window); this could end up either raising or lowering window.
All toplevel windows may be restacked with respect to each other, whatever their relative path names, but the window manager is not obligated to strictly honor requests to restack.
Make a button appear to be in a sibling frame that was created after it. This is is often necessary when building GUIs in the style where you create your activity widgets first before laying them out on the display:
button .b -text "Hi there!" pack [frame .f -background blue] pack [label .f.l1 -text "This is above"] pack .b -in .f pack [label .f.l2 -text "This is below"] raise .b