This is similar to brass rubbing... By rubbing a hard wax crayon over a thin piece of paper that is placed on the bark of a tree the resulting patterns may be compared or used as a recognition tool. All of these patterns are to the same scale.
Notice has to be taken of the age of the tree, the bark of a fifty year old Horse Chestnut tree will different to that of a ten year old specimen. Even in Winter a tree can be recognised by it's bark and overall appearance. Sr. Catherine uses a particular set of trees in her locality, that she has marked, for reference.
Sr. Catherine also uses a fold out chart of 'The Trees of Ireland'. As yet I am unsure of copyright in respect of this item, but it may appear later as a sub page if I can obtain permission. There is a link to the 'Tree Council of Ireland' at top left for further information.