The Figure Four is a submission hold in professional wrestling.

1) Victim is lying on his back, prone.
2) Executor lifts up one of the victim's legs.
3) Executor turns around outward while still holding the victim's leg, which has the effect of bending that leg at an acute angle and placing it inbetween the executor's own legs.
4) Executor sits down on the mat. At this point, one of the victim's legs should be straight, while the other one is crossed over the straight leg's knee, perpendicularly to it (in the shape of a "4", hence the name of the hold). In addition, one of the executor's legs is crooked under the loop of the "4".
5) Executor takes his free leg and places it on top of the victim's crossed ankle. This locks the hold in place.

For some magical reason, the pressure is reversed if the victim manages to roll himself and the executor onto their stomachs. It's total balderdash, of course, but it's just one of those times in wrestling when you have to suspend your disbelief and just go with it.

Ric Flair uses this hold as his finishing move. Greg Valentine also used to use the Figure Four. A few wrestlers (most notably The Rock use it today, but not as their finisher.