http://developer.gnome.org/projects/gup/hig/2.0/toolbars.html

Maybe the HIG is not the ideal place for this (i think this should be fixed in
gtk once and for all) but all Gnome developers should include HandleBoxes on all
their toolbars.  

Although it should be blocked by bug 172300 (provide UI to access the existing
pref and set it off by default) developers should probably also provide
HandleBoxes for menu bars, for consistency and in preperation for time when GTK
has much better docking (bug 111509).  


Recently developers have take a dislike tool handleboxes and started killing
them off.  
Instead they should be using the gnome-ui-properties (a capplet from Gnome
Control Center)

In light of the general developer and user dislike of these widgets and the
annoyance of accidentally rearranging toolbars it has been suggested that it
might be best to disable detachable toolbars by default.  

This topic has been discussed at length on the usability mailing list
 http://mail.gnome.org/archives/usability/2005-March/msg00075.html