Summoning Jutsu

Basics
Summons are typically called forth in a puff of smoke with the Summoning Jutsu or any number of variations thereof. Before a summoning can be performed, the user signs a contract with their own blood, each contract differing depending on what creature is to be summoned. Once this is done, the summoner need only perform the proper hand seals and offer a few additional drops of blood with the same hand they signed the contract with to perform the summon. The amount of chakra offered at this time is directly proportionate to the size of the summoned creature. Summons have their own abilities that they can use by themselves or in conjunction with the summoner. Some summons are so powerful that they may even challenge the summoner, or will demand something in order to contribute to the battle.

In certain cases, it is also possible to summon inanimate objects, as Orochimaru and Sakon and Ukon do with the Rashōmon gate. As with living summons, inanimate summons also require a blood sacrifice.

Examples
Many ninja are capable of summoning animals, plants, and objects. Examples include Naruto, the Fourth Hokage, and Jiraiya summoning toads, Orochimaru, Anko, Sasuke, and a select few of Orochimaru's other former apprentices being able to summon snakes, and Tsunade being able to summon slugs.