Fūinjutsu

are a type of jutsu  that seal objects, living beings, chakra, along with a wide variety of other things within another object. Fūinjutsu can also be used to restrict movement or unseal objects either from within something or someone.

The presence of a seal is marked by the appearance of formations of technique formulae, kanji, or else other kinds of symbols (likewise with Summoning Techniques).

Trivia

 * An imbalance is created when an odd-numbered seal is placed on top of an even-numbered seal and vice-versa.
 * The shinobi from Uzushiogakure in the Land of Whirlpools were specialists in the art of fūinjutsu, to the point that their nation was eventually destroyed due to the fear others had of these techniques.