There are three main styles of whip finishers.
The Matarelli whip finisher, Thompson whip finisher and your fingers.
If your flies unravel, usually due to a bad knot tied on the finished fly, you might want to try using this tool.
Much easier to use than the Thompson and after a few test knots you should be well on your way to mastering the Matarelli Whip Finisher.
Once learned, the knot can be made in a matter of seconds.