Sharing saves memory when the same user-interface object appears in several places.
The example they discuss is a Save dialogue which is used in several submenus and must be set up differently depending on the submenu it is accessed from. Joost thinks there are some problems with Paul's solution. Please note that this discussion was originally posted to comp.sys.acorn.programmer. Joost kindly provided an HTML version of his first posting but the others have been hastily converted to HTML from plain text.