This is a plastic frame for a simple restive current shunt. It was designed to use 5 inches (125 mm) of 18 gauge copper wire, with voltage sense points at 3.759 inches (95.47 mm) to achieve a 2 mohm resistance. The solder points of the voltage sense can be moved slightly to "calibrate" it to exactly 2 mohm. The two large screws are M4, the smaller M3. Corresponding hex nuts fit on the back side. I soldered the wires to small copper sheets for the screw terminals, but bending the copper wires around the screws should also work. The spacing between the voltage sense solder joints is what is critical.

I also modeled in four screw bosses that can be used for a small voltage amplifier or ADC PCB if desired.

The four corner holes are M3 clearance holes.

The wire should handle 20 amps before self heating becomes an issue (20 A = 800 mW dissipation). I've included a version with no text in case someone wants to make one with a different resistance (75 mV full scale is common).