You will need:
scrap woods from the other projects.
black screws for wood
one strong cord (the best is metal string)
A4 paper and strong wire for paper gliders
How to make:
First prepare the stand for a crossbow. This can be done from the scrape of woods.
Then create the sliding board with launching mechanism for paper gliders.
Now take the slim piece of desk and make bow of it.
In the end connect the bow to the sliding board.
Now You are ready to fire Your paper gliders.
Paper gliders for this balista are made like normal one with one difference. They need some plasticine and a strong wire to create hook for the bow string.
All of it is described in the video.