Menustrip class is the base class for MUI's object oriented menus. Its children are objects of Menu class, each of them describes exactly one menu.
A Menustrip object doesn't feature many options itself, but as a subclass of Family class, it simply acts as father for multiple Menu objects.
The Menustrip object is usually specified as a child of either Application class or window class with the attributes MUIA_Application_Menustrip or MUIA_Window_Menustrip.