This is the center point where the binding shows. I didn't have any of the normal binding thread so I used double strands of waxed dental floss. This was actually cinnamon flavored (!) and very old but...it worked. Never stop for lack of the 'right' tool. Improvise!
Finally a larger view of the photo of me on the cover. Taken ...uh...about 68 years ago. I have a lot more hair these days and wear considerably more clothes. That waxed dental floss was a royal pain to sew with here as well as trying to stab the thick paper but once again, it got done.