This kinjutsu that was passed down in Iwagakure allows the user to knead chakra into materials. It is likely that the mouths on the user's palms and chest are a direct result of using this technique.
Deidara violated the law and stole this technique in his quest to find the ultimate art. He used it in conjunction with his Explosion Release, to infuse explosive chakra into clay, creating his Exploding Clay. Clay wasn't the only substance he could infuse his special chakra in, as seen when he ate some of Gaara's sand and made it explode.[2]
