This add on for Blender helps in the creation of rings with text written on them.
They are used to mark birds when they are young.
Blender add ons are nothing more than python scripts stored in scripts/addons/ within blender's configuration.
Download and zip the ring_ruler directory in this repository. In Blender, go to "Preferences -> Add-ons" and click "Install".
A file browser pops up. Pick the zipped version of the ring_ruler directory and hit "Install Add-on".
Blender will automatically unpack the zip and store all files at the right place in scripts/addons/ring_ruler.
In Blender, search for "Ring Ruler" or go to "Object -> Ring Ruler". A helper window with settings will pop up.
The rings are created in original size (millimeters) scaled by a scale factor (usually 1000). The default cube measures 1x1x1 meter, so it covers the created rings if the scale factor is 1. Delete/move it and zoom towards the center.
You can choose a custom font in the drop down menu. The font must be loaded, do this by going to a text object and loading the font there in the "Font" tab.