The rule of nines is used when dealing with burn victims to determine what percentage (roughly) of the body has been burned.  It helps them figure out how to treat them and how much fluid they’ll need.

To clarify, in the parenthesis, it specifies sides.  This means that, for example, the entire head counts for 9%.  However, one entire leg counts for 18% because each side of it is 9%.

Poor thumbs up guy. At least he stays in good spirits.