This optical breadboard is a low-cost alternative to aluminum breadboard. It is meant for budget labs, start-ups, teaching, demonstrations etc. Inspired by a metric version openOptics breadboards, but I needed imperial ¼" threads. The underside has designated hexagonal holes for ¼"-20 nuts (like these). The nuts are meant to be forced into place (tight clearance) or heating them using solder iron. I compiled several useful hole configurations, but sharing also the source code *.scad file if anyone needs a different configuration (just change N_x & N_y variables). 

Technical details:

PLA @  on 0.4 nozzle bambu lab A1. Sliced on bambu studio on standard settings 0.2mm z resolution. If supports are not used, the hex nut holes can turn out fibery (does not influence usability).  I recommend printing first layer slow ~20mm/s.