The Trap Guard is a great tool to have in your game, especially if you don't like playing traditional closed guard. It keeps you safe (even from punches) and will set up a ton of attacks and sweeps.
In the final part of the series, Professor shows how to use this to set up your own arm triangle. This can work as either a finish or a sweep and once you get the arm transition down, it's pretty easy to set up. And if nothing else, it gets them more tied up than ever!