|Please note that this is the Narutopedia's article on the threads used by puppeteers. If you are looking for the article on the Fūma clan suicidal technique then you should head to Chakra Threads.|
These strings are constructs made from very concentrated chakra so, they can be seen by people besides the user. A skilled user can suppress the chakra to the point that the strings become invisible, as Chiyo did with the Manipulating Attack Blades to sneak a string to bind Hiruko's iron tail. These strings essentially act as an extension of the user which allows them to manipulate whatever is attached to their strings such as hidden weaponry in a puppet as they please. Chakra can also be transferred via the strings, such as to activate justu that the puppets can use. The chakra strings can also be attached to other objects, allowing the user to control, or at the very least disrupt other things.
In one instance, Kankurō uses chakra strings to trip Naruto Uzumaki when they first met. In another, Chiyo uses chakra strings to control a person like a puppet. Kankurō has shown the ability to attach his chakra strings to those of another user's. This technique is limited to one main string per finger for normal humans, but Sasori's modified core was able to emit enough strings to control over one hundred puppets.