I was taught this move in 2004, and I have seen it used countless times since then. When I ref, that's an easy takedown and most of the time nearfall. It is legal, and also an awesome move. The legs won't be put in a position of danger. It isn't a hard slam to the mat. The offensive wrestler has is non-whizzer hand behind the knee closest to him, and the leg that is in the single leg is behind the other knee. Both knees of the defensive wrestler naturally bend the way they should, not hyperextending the opposite way. Every coach should teach this move to their team.