SAO biscuits are a savoury cracker

Cracker (food)

A cracker is a baked good commonly made from grain flour dough and typically made in quantity in various hand-sized or smaller shapes. Flavorings or seasonings, such as salt, herbs, seeds, and/or cheese, may be added to the dough or sprinkled on top before baking...

 biscuit that was launched in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 in 1906 by Catherine Sao. The term SAO was trade marked in 1904.

SAOs were also one of the first biscuits to be heavily advertised in magazines and newspapers in the early part of the 1900s. In the 1960s, the famous SAO song was launched. SAOs light texture is achieved by rolling the dough into thin sheets, then carefully layering it to give distinctive bubbles and crumbs.

SAOs are often eaten as a light snack, topped with butter/margarine and Vegemite

Vegemite

Vegemite is a dark brown Australian food paste made from yeast extract. It is a spread for sandwiches, toast, crumpets and cracker biscuits, and filling for pastries...

, or other ingredients.

Traditionally, Arnott's delivery vans have had number plates (license plates) in the range SA 0nn in recognition of the SAO brand.