Correct. The fly is tied ON THE TUBE and then, when you are ready to use it, you slide your tippet through the tube, attach the hook of your choice, and slide the tube down over the hook. Fish strikes the tube, fish gets hook instead, tube slides up the tippet, fish is landed, fish is admired, fish is released, tube is slid back down over hook, and fishing continues. Tying flies on tubes allows the angler to tie a large fly and then use a small hook.

The Chronicler