Final answer:
The 'rule of nines' assesses the amount of body surface affected by a burn by associating specific anatomical areas with a percentage that is a factor of nine. This helps in making decisions about the need for specialized treatment.
Step-by-step explanation:
The 'rule of nines' is a system devised to assess the amount of body surface affected by a burn. This rule associates specific anatomical areas with a percentage that is a factor of nine. By determining the percentage of body surface area affected by a burn, medical professionals can make decisions about the need for specialized treatment.