A tree tag is a string of letters and numbers to describe a climbing tree in climbers' shorthand. Here's a breakdown of a tree tag. 

• The first part of the string is the tree's name: McCrutchen.

• Difficulty rating is next: McCrutchen Class 5.

• Add a numerical character beside the class number to be more precise: McCrutchen Class 5.9.

• To end the tree tag, add the time commitment: McCrutchen Class 5.9C.

   

There it is: McCrutchen 125 Class 5.9C. To most, it's a string of senseless numbers and letters. To a tree climber, however, it's quite useful. The tree tag described here tells climbers they'll be climbing "McCrutchen;" the tree will present them with a Class 5 climb, a difficult climb, and it's going to take all day to do this climb.