Recently I replaced my son's bar mitzvah tefillin with a better quality set. The head tefillin was tied for a small head size and needed to be expanded to fit my son (he's quite a large young man now!). As I was gently trying to adjust the dalet knot this morning without losing the knot completely... SPROING! It all came apart. Imagine my concern about having to tie the knot back together. This is not a simple knot.
I found this wonderful video on You Tube showing how to tie the dalet knot on the head tefillin and though I would share: https://www.youtube.com/watch?v=KLBm6k8QHqU . I pray it will be as much a blessing to you as it was to me! :)