Multi-purpose tool by Prof. Dr. Claus Mattheck and Dr. Klaus Bethge The stainless steel model is an multi-purpose tool for tree diagnosis. This tool measures the slenderness of tree trunks and branches. It may also be a non-dogmatic guide for shaping the crown of a tree according to the shape of brook pebbles. The model can show the highly loaded space under the tree determined with the force core method.