Black colour denotes protection from the evil eye. A black thread is usually tied to the waist of small children to protect them against 'nazar' or evil eye. This can also be tied on Right wrist of men and left wrist of women for protection.
Black thread is also tied to overcome fear.
If you are suffering from nazar dosha , then wear this on wrist after rolling this on wrist clockwise seven times and tying with seven knots.
This is 100% cotton thread.