These will accept an M3 nut and then drop into the slot in a 20mm profile t-slot aluminum extrusion (incl. MakerSlide). No need to slide in and out from the ends of the extrusion! Insert a screw and turn clockwise to tighten and it will turn 60Â° to lock in place. Turn counterclockwise to loosen and it slips right out of the slot. I have only tested it with 20mm and 25mm profiles, but it's parametric, and should work with any profile larger than 20mm. If you find settings that work well for other profiles, let me know and I'll update the files.
These are tiny, and the first few iterations didn't work because there was too little material to reliably produce the shape. You'll want to print a lot of them at once for cooling purposes, and the scad file has variables for duplicating it along the X and Y axes.