I created this tool to help calibrate the tool offset between my two extruder. This design was inspired by this thread http://forum.makergear.com/viewtopic.php?f=13&t=2747 This is a Vernier scale, where each line represents a shift of 0.05 mm. Print this with two extruders and see at what point in the scale they align. If your offset is exact the alignment should be around the middle (long) line. It is still hard to read the exact offset, but the example in the photograph I believe that the white should move about ~.1mm to the left (the current distance is too long, as the white is the right extruder).