These files are used with M8 threaded rods or Lead Screws to create a framework that you can hang paper or cloth from to create a seamless background for taking photos. The nice thing about this is you can make the backdrop as large or as small as you need it depending on what size rods you use for the height and width of the framework.

Base.stl and nut.stl and designed for regular M8 threaded rod; while base2.stl and nut2.stl are designed for M8 lead screws (which is what I had handy).

NOTE: the pictures show a framework based on 600mm rods, so scale to your heart's content.

I used STLs found here to create some parts of this rig:
https://www.thingiverse.com/thing:1954719
https://www.thingiverse.com/thing:5996707