Okay! So the movie was fiction: they just tacked it in place with glue or tape, shot the scene with him pulling it out, then glued it back in place for the next big-knife-pull-out scene.

And thank you, Knife Guys, for all the other responses from and for real life. I kind of thought there were ways to do it, but I don't depend on Hollywood for truth, since they can't even spell the word.

One more "I wonder how..." laid to rest.

Sue