Sounds intimidating? Not! They're really simple, once you get the hang of them. I had a really hard time finding instructions for these anywhere, so once I was able to piece together the technique I decided I had to put up a tutorial at some point. So the rest of you can see how I do it, at least. It's such a nice touch for casebound journals.
Step one - use masking tape to secure your headband core along the upper edge of your book block. This picture actually shows the core a little farther away than it should be - it should sit right across the top corners of the pages. But don't worry about it too much - the sewing will pull it into the right place.
Find the top sewing hole of your first signature and thread one needle through it. You might have to poke your needle through from the other side first so you can see where that hole is. Pull the thread through to the knot.
Can you see how that thread goes? It's through the top binding hole, up along the inner spine of the first signature, behind the headband core, and forward across the top of the core.
Here we go. Wrap the thread around the core once. You should be wrapping away from your body. I'm using Black and White, you might be using different colors, but for the sake of simplicity I'm going to say Black and White. Hold your Black thread taut with one hand, and thread the needle of White behind Black right where Black peeks out of the top of the signature.
Now bring your White needle up behind itself. You can do this differently if you like - you're basically knotting the white thread around the black to secure it before you start the actual sewing of the headband.
Once you have the White thread knotted there, thread the needle under the core and lay it over the top of the black thread, like this:
Just hold everything there and take a good look at what you just did. This is important - if you don't start correctly, it won't work, and it's hard to take it all out. So check that everything is tight and secure.
Next!
I forgot to take a photo here, but fortunately this step is easy. Thread the needle back under the core, toward your body, and then wrap it around the core like this:
During that second bit, you will be looking at this:
You can see that the black thread is pinned down to the core by what you just did with White, not just laying over the top.
So at this point, your White should come from its knot at the beginning, under the core and around the FRONT of that Black thread to pin it to the core, back under the core, over the core, under the core and over the core again.
Next!
Now do it again - bring Black over White, and then thread the Black needle under the core toward your body. If you did that right, the Black thread should pin that white thread to the core, then go under the core, and hang down along the book spine. Then...
Find the signature nearest your working point and stick the Black needle through the top sewing hole!
Now thread that Black needle under the core again, so the Black thread wraps around the core.
Pull the black thread taut along the top of the pages, and... can you guess? Bring the white thread over it, to the left, pinning it to the core. Then thread the White needle under the core towards your body. Then under the core again and over so it lays along the top of the pages.
Repeat this until you reach the end of the core:
Black thread to the left over White, thread needle under core, over core and through signature hole, up along the back of the spine and pull taut over the core.
White thread over Black, thread needle under core, over core, under core, over core, pull taut.
When you get to the end, it should look like this:
And you can see that in the picture above, instead of threading the needle under the core, to the left, after I come out of the signature, I'm threading it under the core but to the right, between my last two stitches.
Once again, you can do this differently if you like - you're basically just knotting the black thread to secure it there, like this:
See? I just make a loop and knot it here. I think it's simple and quite secure, but if you find it works better a different way, let me know. :)
Then I bring the Black to the other side and knot it there, too.
Do the same thing with the White, knotting on both sides, so it looks like this.
And when you spin the book around so the page edges face you, it should look like this, with a nice little bead on the edge:
Ta-da! That's it! Very simple. I hope this has all been clear. Please feel free to ask questions in the comments! :)
Good luck!