These fixture plates are designed to produce softjaws that allow for holding an 80% AR15 lower receiver to machine the trigger group pocket. Also, depending upon how produced it can provide guide bushings to drill out the three holes in the trigger group. Was created with AutoDesk Inventor 2014, if you want to modify the files, the original code is provided. For those of you with other 3D CAD software I am including IGES files of each model, which should be compatible with most software (including FREECAD).If you decide to 3D print this, the stl files are in inches, so you will need to scale them up by 25.4 Also the stl files should be rotated so that the y-axis is 'up' on your machine. Other then that, they do not need support to print. If using a 3D printed fixture for machining, I suggest that you have thick shells (say 1-1.5mm) and a pretty high density. I produced with 50% fill, and it seems to work fine. You do need two alignment pins to register the two plates with the takedown holes on the AR15