200mm x 200mm optical breadboard with M6 and M3 holes, Metric Standard 25mm and 12.5mm apart. 3D printable with M6 and M3 nuts inserts. Use Cura with the ''Pause at Height'' plugin to set the printer to pause at 8.55mm height, move the nozzle out of the way with the software (not with your hand), insert the nuts in their holes, skirt a bit of filament and press play. Or you can find the layer height in the G-code and insert a Pause command line there. OK now, one of the models has so many screw holes is probably overkill and will affect the structural integrity of the breadboard so I made another one with less M3 holes. Recommended settings: Set the vertical walls to minimum 2 pass thickness; Set the horizontal walls to about 1mm thick; Set the infill to about 15-20% Download the SketchUp model attached to customize and adjust your tolerances, this one was optimized for the machine we have in our lab.