The purpose of this head is to allow you to rotate your camera about its nodal point / exit pupil, letting you take a series of photos in all directions, without any parallax error.
Once you take the photos, you can process them through various pieces of software to produce a single image that can cover up to a full 360° - including the ceiling and floor underneath you.
I made my head primarily out of 20x20mm T-Slot aluminum that I purchased from Misumi. Instead of designing it all in advance and having Misumi ship me the precise correct length pieces, I have a couple meters of the material that I keep at home for various projects like this.
Fabrication of the head involved cutting the T-slot material to the right length, deburring / polishing the ends, cutting a few holes, and tapping screw threads into a piece of steel for attaching it to my tripod.
I made it in the metal shop at TechShop