This is one of my most popular projects! You'll be surprised how far this crossbow shoots. At least 50 feet! You will need a bandsaw, drill press (ideally), and whatever sanders you have...there are a lot of curves to smooth out. 

You will also need a 5/16" dowel and some Theraband material. Or you can just get an exercise resistance band at a sporting goods store. And of course, some mini-marshmallows!

Watch the how-to video carefully. That will help you understand the plans much better. 

How-to video:

(Watch on YouTube)