MakerSlide or 20mm extrusion parallel joiner

Joiner to connect 2 MakerSlide rails together. I designed these to allow me to double up the X rails on my ShapeOko CNC machine. In addition to the MakerSlide rails, these should also be compatible with 20mm extrusions from Misumi, Maytec, Alufab, Bosch Rexroth, Easy Systems, and 80/20 Inc.