Note: This version is threaded for common imperial ¼"-20tpi screws. I have uploaded a modified version threaded for Metric M6x1 hardware for use with fiber lasers and metric threaded tables which can be found here: "Renzetti Style" Connectible 1-2-3 Blocks v2.0 \ Setup Blocks (M6x1 threaded version) by Emoticon - MakerWorld

These are machinist 1-2-3 blocks, but they have 1001 uses for all sorts of fixtures, jigs and now with threaded holes they can easily be connected together like a building set to make whatever you want. 3D printed 1-2-3 blocks are better than no 1-2-3 blocks and 3D printed Renzetti style ones are even better. The outside dimensions are 1"x2"x3" the holes are threaded and chamfered to accept ¼-20 cap screws, but button head ¼-20 machine screws will work as well. These could also be great as a “purge to model” print to make when making other things or just running out the end of a spool.

I designed them after seeing this video here where OxToolCo shows off making his own and credits the original inventor, Robin Renzetti. You can see the video showing off their use here: