The majority of the protective overprints and underprints appear on the stamps of Queen Victoria.  As there are so many I have had to split the outline images across several pages.  The table below explains which underprint outline type is on which page.  That way, if you know which one you are interested in you can navigate to it more easily.

* Unlisted items have, obviously, not been allocated a type or catalogue number by Stanley Gibbons.