nut5 use flat M5 nuts with this in 5mm 20x20 extrusions T-Slots

thingiverse

I use these substitutes to secure regular M5 nuts in place due to the original ones being too expensive. They are designed to be snugly fit, so you may need to experiment with sizes ranging from 98% to 102%. Simply push the nut into position using a round object of similar size. If the part cracks under pressure, it's likely the nut is too tight; if the nut slides in easily, it's probably too loose. I utilize DIN 439 M5 flat nuts measuring 2.7 x 8mm for this purpose. Print Settings: Printer: Hypercube Rafts: No Supports: No Resolution: 0.2