Siphon overflow diagram needed

[bluetang]

Hi folks, I'm looking for a actual diagram of a DIY overflow box for a smaller tank(20g). Ive seen some pics of actual unit but not to many diagrams. Preferably something that encompases a devise that prevents emptying my tank on the floor. Anything would be a great help as i am strugling to find a design that will be sutable for me. My tank is not driled so it would have to be the siphon type. If you find a few different types please post them as hopefully this can be a thread for everyone to use.
thanks
rob