Scrolls are used for quite a few different reasons. Many ninjas use the scroll for summoning natural substances such as water and it could also be used for summoning weapons. Scrolls can also be used to trap things inside as seen with Jiraiya.
Scrolls, apart from apart from being things to write on, can be use for many ninja help skills, for example, Tenten uses her scrolls as a partial summoning, when needed she pulls out her scroll, sets her mark, and then summons thousand of shuriken, kunai and throwing needle which are controlled by her chakra. Scrolls can also be used as a trap, this is best shown in the "Forest of Death" stage of the chunin exam, when if both scrolls needed aren't opened together a Jonin is summoned and either renders the shinobi unconsious or congratulates them (if opened at the end of the stage).
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