Four Symbols Seal

This is a sealing technique based on the the fūinjutsu of Uzushiogakure.

When two Four Symbols Seals are used together, they form the Eight Trigrams Sealing Style. When Minato sealed the Nine-Tailed Demon Fox into Naruto Uzumaki, he left an opening at the space where the two four symbols seals meet, allowing the Nine-Tails' chakra to merge with Naruto's chakra. Minato also left behind a key with Gerotora, which would be used to tighten the seal when it weakened. Naruto would eventually use the key to gain control over the Nine-Tails' chakra.

The seal also usually appears on the stomach of the users of the Dead Demon Consuming Seal after their target (and the user's own soul) is sealed in the death god's stomach, such as what happened to Hiruzen Sarutobi after sealing Orochimaru's arms.

Trivia

 * This is a high-quality seal and according to Killer Bee is more durable compared to the Iron Armour Seal that holds the Eight-Tailed Giant Ox.
 * This seal is the opposite of the Reverse Four Symbols Sealing Technique.