Janeu, also called Yagyopavit, is a sacred yarn that is worn which is made up of cotton which is worn n the left shoulder under the right arm. You must have seen many people wearing a white cotton thread on their left shoulder, which goes under their right arm, this is called Janeu.
It is said that every hindu has a right to wear Janeu at the right time in their life and follow the rules and regulation of the system. There are three types of Janeu, for Brahmcharis, the janue should only have three threats kneaded together, and for married men, there should be six threads, even women cane wear janeu.
Once you wear the Janeu it is not to be removed from the body. If it becomes sloppy of any of the thread breaks, then the Jnaeu should be changed immediately. Always cleaning the thread and keep rotating it everyday that is also one of the rules of wearing the Janue.