Yeah, the kids deserve to see Dad in action using their gift.
I have a set, but seldom use them. The hole is sized to accomodate the the eye of the hook. Obviously, once the guard is in place, never build a head so large as to prevent you removing the tool.
After you have wrapped and locked your hackle: With the bobbin on a dangle, slide the tool onto your thread via the slot (radius cut). Slide the guard up the thread, over the eye with the concave surface facing your hackle. You will now be off the thread with the tool resting on the shanks thread base. You may weight the tool at any time as desired to prevent rolling. Build your head, whip finish, remove the tool and cement.
Practice a few times then call the kids in.