Sanchin Stance is a stance used in karate and can be considered as one of the most important techniques. The way the feet are placed and the muscles are tensed, provide a very stable position.
One of the important uses of the Sanchin Stance is protecting the crotch. The upper leg muscles are providing a sort of shield, making it inpossible for an upward kick to hit the crotch as the kicking foot gets stuck between the leg muscles.