90 deg. angle for 20 x 20 extruded Aluminum

While building a Core XYZ frame I found that the surfaces where two Aluminum piece's met were not always aligned with each other. This made alignment of the two ends of parallel rods hard. So I put this part on all joints to keep the surfaces aligned with each other. There is some structural strength but not much. The primarily purpose is to make sure the surface are aligned. You will still need to support the joints with 90 deg. angle buckets.

Both the printer file and the source file a