Once you've finished debating which superhero you'd want as a best man (Iron Man blatantly) and which side of the bed is more preferable (trick question - the middle), chances are you'll usually swing back to whether toilet paper should hang over or under.
After hours of intense, often incredibly nasty, discussion you'll probably wish that someone would just go ahead and make a damn infographic about the whole subject.
Well, after enough scientific research to make the whole concept of education seem invaluable, the folk at Engineering Degree created this worryingly well-researched image, bringing together everything you needed to know on the eternal battle.
Whether you cared or not.
(Top Image: Rex Features)