I came upon the Orvis Tippet Knot (aka the figure eight knot) as I was exploring the deployment of multiple flies on your leader when fishing stillwaters. Using dropper tags rather than tying a trailer fly to the bend of the upper fly's hook is preferred by a number of well-credentialed anglers, and I wanted to give it a try. I have't fished with this setup enough to have an opinion of it yet, so that's not the topic of this post. Instead I'm just presenting the knot tying element of the system.
There are any number of knots used to tie dropper tags. The first I discovered is the double or triple surgeons' knot. You simply add the dropper tag to your normal tippet by laying it alongside the tippet and tying the double or triple surgeons' knot using the two lines as if they were a single line. It's been used with great satisfaction for years by a lot of good anglers. Still, I ran across some posts where people complained of their dropper tag breaking at the knot when using the surgeons' knot. As an alternative the Orvis Tippet Knot was suggested. I've practiced tying it, and it seems a good knot, but I had some trouble negotiating the necessary movements with my fat stiff fingers. The video I'm posting here uses your hemostat instead of your fingers, making the tie a lot easier.
While I came across this knot while thinking about dropper tags, the Orvis Tippet Knot is just as suitable for the more common practice of adding tippet to the butt section of your leader (just as you can do with the surgeons' knot). Give it a try if you feel so inclined, and give feedback if you have any.