Here's some plans for you: http://www.backwoodshome.com/articles/sanders64.html

I haven't built one of these, but it looks sound. I will say if you ever have intentions of building one for catching coon, you'd best use screws, construction adhesive, and astrong mesh on the back. They are amazingly tenacious and powerfully strong. I had a medium sized coon take a 1/4" steel trigger rod in a commercial trap and tie it in a knot.