In order to set the x axis parallel to the frame, I needed a tool to easily repeat the elevation of the 20x20 extrusion on both sides of the printer. With this simple tool, I set the elevation of the gantry to the correct height on the left side until the tool is just touching over the extrusion and then I check the other side. I have retrofitted to a dual z-axis motor and also belt-pulley system, so I now have great control and repeatability.