A Tailed Beast is sealed inside a person using a specific type of seal, to make them a jinchuuriki. While, some seals have been revealed in the series, other haven’t.
I’ve managed to gather 7 different types of seals used on Jinchuuriki.
7. Iron Armour Seal
The Iron Armour Seal is Kumogakure’s special Fūinjutsu used to seal the Gyūki into its Jinchuuriki. It was used on Blue B and later on Killer B. This seal was manifested on Killer B’s shoulder. This seal is also said to be weaker than the 8 Trigrams Seal.
6. Gaara’s Seal
Granny Chiyo used an unnamed sealing Jutsu to seal the Shukaku into the baby gaara, who was still inside Karura’s womb. Gaara was the only child of the 4th Kazekage who was compatible with the Shukaku. As a result, Gaara was born prematurely, which led to Karura’s death. This sealing Justu isn’t really helping at all for the Jinchuuriki, as Shukaku was able to take control of Gaara’s body when the latter slept. As a result, Gaara wasn’t able to sleep at night which is probably why he has the dark circles around his eyes.