Science Buddies: "Ask an Expert"

hello,
i am wondering, why would i use a chopstick this project.( Do Submarines Need Fins?) found in the search box..

Here's what the chopsticks are for in the project "Do Submarines Need Fins":

https://www.sciencebuddies.org/science- ... #procedure

Making the Submarine

To make the submarine, have an adult drill two small holes in the bottom of the water bottle, just like the holes in the propeller—one in the center and one slightly off-center.
Straighten one end of the second paper clip and use chopsticks to insert the straight end of the paper clip through the hole of the water bottle, from the mouth of the bottle into the centered hole at the end of the water bottle. This step is tricky!
Once you get the straight end out, use the pliers to bend the end over and hook it into the other off-center hole to secure it.
Use the chopsticks again to hook a rubber band onto the paper clip hook inside the water bottle submarine.