Shinobi Gauntlet

The is a  developed by Katasuke of Konohagakure's Science Ninja Weapons Team.

Overview
As its name suggests, this tool is worn on the forearm. The user initiates one of their techniques before sealing them into a scroll. The scroll is then shrunken to pill-size and is put inside the Kote. Afterwards, they can release the scroll and use the sealed technique. To use some elemental technique, the user apparently needs to form the corresponding seal first. Because using the Kote doesn't require chakra, the user can gain an advantage in battle by releasing normally chakra-taxing techniques while saving their chakra or continuing to use techniques when low on chakra, thereby keeping the user rested and less-likely to endure exhaustion; it can even be used by a non-ninja person.

Sealed Techniques
In addition, in the novel version of Boruto: Naruto the Movie, Katasuke was able to launch an attack at Momoshiki Ōtsutsuki using techniques of the Ice, Lava, and Wood Release kekkei genkai, and hiden jutsu, collected from various clans of Konohagakure.
 * Crimson Flame
 * Fire Release Bullet: "Blaze"
 * Lightning Release Bullet: Powerful Breath
 * Rasengan
 * Shadow Clone Technique
 * Shadow Imitation Technique
 * Thunder Splitting Heaven and Earth
 * Water Release Bullet: Orca

Trivia

 * Masashi Kishimoto thought of a tool like this since before Naruto began. However, he could never introduce it into the manga.
 * The Kote also seemingly improves a technique's capacity, as Konohamaru's usage of Rasengan through this device allowed him to launch the normally-handheld technique a great distance away as a projectile.
 * When Konohamaru sealed the Rasengan, the kanji for appeared on the scroll. Afterwards, he also used the Wind Release hand seal when he launched the Rasengan, despite it not being a Wind Release technique.
 * Kote are currently banned from the Chūnin Exams by the Seventh Hokage, Naruto Uzumaki, stating it would be unfair for others who worked hard.