MB is a set of tools designed to make accurate polymodelling quicker and easier.
It is currently developed for Blender 3.3.4 LTS, but can work for other versions.
It is not recommended to download the repository directly to install as an addon. Instead grab the latest stable release here:
https://github.com/JohnKazucki/JD-Miter-Box/releases
Can always be found here: https://github.com/JohnKazucki/JD-Miter-Box/wiki