I actually tie them a little differently than the links listed above. First, I use a long shank hook, like a Tiemco 911 or Mustad 34011 (or the sig series equivent --70S or something). I tie them the same way I tie a hollow fly, but without reversing the bucktail and with maybe more collars. For a hollow, I might tie 3-4 collars reverse tied, while for a BD, I might tie 5-6 with the tips of the hair facing back to start with. In Bob's book, I think the example has about six collars. Basically starting at the bend, you tie in successive collars of bucktail surrounding the shank, spaced a little farther apart in the beginning and getting closer together as you approach the hook's eye and also using shorter lengths of hair as you move up the shank. I surround the bucktail with flash between some of the collars and then use either tab prismatic eyes, or, if I'm feeling fancy, jungle cock eyes. Then, run the whole thing under hot water to shape it. The whole thing has a kind of tubular shape and ends up a little denser and less wide than a hollow fleye generally. I'll bring some of both to the Fling if I make it. I tried posting pics, but I got messages that my file was too big -- too many bytes or something. I need all the bites I can get!!!!!!