cajon is a drum originally from Peru. It is almost always made out of plywood and produces different sounds depending on where you strike it. Some (like mine) have snares inside, some have guitar strings stretched across the inside, and some are simply hollow. They all have a hole in either the back or the side (like the one pictured) to create a deep bass drum sound when struck in the center.
Bill Wilson got me curious about cajones a while ago. The more I looked into them and researched their construction, the more I wanted to build one. Here are a couple that he's made. Bill really helped me out along the way with techniques and cluing me to all the various ways they can made.
If you are interested in making your own, here's some in-depth instruction including a video showing the cajon in action.
Here's my version: