Fūinjutsu

are a type of jutsu that seal objects, living beings, chakra, along with a wide variety of other things within another object.

Sealing is a powerful form of jutsu, to the point that the shinobi from Uzushiogakure in the Land of Whirlpools, who were specialists at fūinjutsu, were destroyed due to the fear others had of their techniques.

Trivia

 * An imbalance is created when an odd-numbered seal is placed on top of an even-numbered seal and vice-versa.