This scroll will teach you how to learn this technique called Multi Shadow Clone Jutsu. This technique is essentially a massive version of the Shadow Clone Technique. Instead of a few clones, it creates a few hundred clones. This is considered a kinjutsu, because it can potentially be dangerous to the person performing it, seeing as how all of the clones are given an equal amount of chakra directly from the user. Naruto learned the technique from the scroll of forbidden seals.
Few people are able to use this technique effectively, due to the large amount of chakra it consumes. However, this weakness is not an issue to Naruto, due to his massive chakra reserves. Having such reserves allows him to create hundreds of clones while maintaining a decent supply of chakra in each one. This technique is also used by Naruto to train quickly, since all the clones share their experiences with Naruto, but it causes extreme fatigue with repeated use.
Naruto is shown to use this technique on multiple occasions to form human chains, for both offensive and supplementary reasons. Now read this carefully, the only way to use this technique is by using a hand symbol ONLY for Multi Shadow Clone Jutsu. This hand symbol is sort of like a cross with your index and middle finger of your right hand vertical and the index and middle finger of your left hand horizontal. If you don't use this hand symbol, solid shadow clones would not be able to develop.