Sliding Bifold Door lock for small kids and cats. I liked the idea of a poll coming down so I didn't have to reach as high to slide the lock back and forth. They were $15 on amazon so I created my own. 

I made it so you could pick up a dowel at any local hardware store. It's designed to work with either 8mm dowel or 5/16 dowel. I glued the dowel in to make sure it wouldn't come out.