There is something that is called "Internal Stretch" where you grab the inner penis behind your balls and with the other hand behind your glans and stretch the shaft upwards and behind the balls outwards. You should feel the internal penis behind your
balls when you grab it. This stretch gave me very fast and consistent length gains, but i stopped it because i was afraid of how it would make my penis look like. I have periods when i'm sceptical about some things.
Or else you meant the Testicle Health Massage, look up the correct link and you can read about it.