When we ran into problems with the Z-axis steppers getting out of sync with each other, we designed this little cap with an indicator on top so we could see if they got out of sync again. Once printed, it simply gets pressed onto the top of the Z-axis screw drives. Just make sure that each one points in the same direction as the other, and don't twist them on - you can accidentally turn the stepper motor if you try. The SCAD file should be fully editable. It was created with OpenSCAD.