This is a photo of me (in red & black) completing a triangle choke during a match at the 2015 Northeast Championship of the North American Grappling Association. My left leg is wrapped around one side of my opponent's neck, and my right thigh is pressing his own arm/shoulder into the other side of his neck. I won the match by submission with 8 seconds remaining.
Want to learn how to choke someone with your legs? Watch this instructional video.