Captain I am not 100% on that expression but I think it means "you don't know your ass (NOTE:-American spelling deliberately) from your elbow"
I checked out the site you mentioned. Quite a few expressions are not quite correctly translated. It should also be pointed out some expressions are associated with particular areas of Scotland and are not necessarily the same throughout the country.
As a quick example the expression "weans" (wee-uns) and "bairns" both mean children but one is more used in Glasgow and the other more common in Fife, but they are not restricted to those areas and both are used throughout.
Here endeth the lesson for today, back to shenanigans
BTW Pearl, has Haggis Season begun yet? It can't be far away. I forget the exact date>
Bains is also used in the North east of England, my parents were from Sunderland and we were always called "the bairns"