This is a small and handy tool for folks building a "Keinachtsbaum". Keinachtsbaum (https://keinachtsbaum.de/) is a sustainable christmas tree alternative: you put freshly cut tree branches into a  central stick with many holes in it. It's basically a DIY christmas tree. The cool thing: you can get those branches from sustainable tree farms where trees are not cut down but only branches are removed. That way, fewer trees need to be cut. And even branches from not-so-straight-grown trees can be used. 

The tool I built helps to quickly measure the diameter of tree branches while setting up the tree. When you cut the branches to fit into the stick, you can try them out with the tool before putting them into the central stick. Diameter for all holes are the same as in the largest keinachtsbaum stick.