Where the Red Fern Grows how does grandpas brace and bit work?

Grandpa would use a brace and cut a small hole in the top. The coon would stick its paw in the brace to get the shiny objecy that Grandpa or Billy placed at the bottom and when the coon would pull its paw out it could not because its paw could not fit through the hole. The coon would be too stupid to let go of the object and would be trapped