Sorry, Bill, I seem not to have seen this when you originally posted it!

A Sao is a dry biscuit - like Saladas or Cruskits (although they might both be Aussie too...) - which were a staple when I was a kid (think I'll have to go and buy some, now I think of it). Here's a link: http://www.arnotts.com.au/Biscuits/OurBiscuitss.asp?BID=42#
(I hope that works) They're about 7cm square, which means that fitting one in your mouth is an effort! And they've got little holes poked in them, like a chess board I guess, so if you have Vegemite (dark brown in colour) and butter on it, and you squeeze the two Saos together as a sandwich - you get worms coming out! Well, it was fun when I was 8...