One of the person will throw a knife at the other one. However, instead of being impaled, the defender will block the knife with a convenient piece of wooden plank. This effect takes a little more setup than the previous knife-in-the-head effect, but is much less gruesome.
Start by establishing your scene by filming both the attacker pulling forth the knife and your defender grabbing a piece of wood. Now, film a side-view of the attacker throwing the knife into a safe (unoccupied) direction.
Here’s where things get fancy. This is a film with the knife embedding into the piece of wood, but we'll run it in reverse when we edit the clips on our computer. Stick the knife into the piece of wood, and attach a string to this knife.
Film the defender holding the board (with knife), and, while rolling camera, pull hard on the string so that the knife comes flying off the board. When you run this in reverse, it will look like the knife flew into the board. To make this effect look more realistic, instruct the defender to rotate the board sideways as soon as the knife comes loose … this will make it look like he blocked the knife just in time.
The tricky part to this effect is getting the knife to stick to the wooden board. I've tried using a sharp kitchen knife (not recommended) and it took quite a lot of pressure to get the knife to stick into the wood, and a lot of pull from a high-test fishing line to dislodge it. Plus, it was a little scary having a sharp knife suddenly unstick from the wood and fly straight at me. So, you might want to experiment with toy knifes and other methods to make them stick … maybe poster putty or clear tape. Also, the string often shows up in the final movie, but that’s ok because it looks funny.
You can perform many other effects by reversing your film. Another knife trick you might want to try is the "knife catch” … instead of using a piece of wood, the defender actually catches the knife. Simply film the defender throwing the knife, and run it in reverse as if he’s actually catching it.
