The file 'Knurling Bolt-Nut Connector 3D Printer Model' is (stl) file type, size is 3.0MB.
Remix of Knurling bolt and nut by akira3dp0
https://www.thingiverse.com/thing:1460364
This part can screw into copies of itself.
I've also included a version with a hole through the center.