With this pen lift mechanism the pen is lifted perpendicular. This enables to draw a straight line on an egg. I used 5mm plywood and a teflon (PTFE) rod for a plain bearing. Drill a hole into the rod so that your pen can easy slide but has not to much room. That is not a simple thing to do. I finally used a lathe to fine adjust the diameter of the pen. I needed a small spring to pull back the pen. Then assemble the parts like shown on the picture.