The Burdizzo is a farm castration tool that quickly crushes and destroys the blood vessels supplying the testicles. After using this tool, the testicles shrink in size and are eventually absorbed by the body. If the Burdizzo is not closed quickly enough, however, the blood vessels will swell and problems will arise. Those that have successfully used the Burdizzo have generally had a friend close it for them. Because of the intense degree of pain, few people successfully use a Burdizzo on themselves.
It should be noted that while the Burdizzo was not designed for human use, articles have recently been published in urology journals noting that on humans, the Burdizzo appears to be both safer and simpler than surgical methods of castration!