Here's a brief overview of the Single Leg Takedown, one of the Freestyle Wrestling staples. The name 'single leg' refers to the grip on only one of your opponents legs, and it's often used in combinations or chained takedown attacks.
For use in BJJ & MMA, it's important that we remember our opponent can attack for options such as the guillotine if we hang our head on the outside of the body. Placement of head on the chest helps us to mitigate that risk.