I know there's a whole bunch of designs like this on here, but i designed it before i knew about this place. i have 3D printed this one myself and it fits together very well.

There is no attachment method to attach more than one of these together, though, hot glue works very well for that. Here's a link of it all together: https://m.youtube.com/watch?feature=em-upload_owner&v=JLBtXR6v48A