Raksha Sutra, also known as Mauli, Moli, Kalawa, Kalava, Nada Chhadi, Wrist Thread. Dhaaga etc. 

It is used in all type of puja (pooja) and Hawan. 

Significance: 

Raksha sutra is an auspicious hindu thread also known as mauli or Kalawa. It is tied on wrist prior to the start of puja is called a Raksha Sutra. Raksha means protection, and Sutra means sacred thread. During puja vidhi, the Pandit ties the raksha sutra on wrist while chanting the mantra. The purpose of the Sutra is to protect us from harm, evil spirits, bad habits, and to keep our minds focus. 

The holy thread when tied on wrist, represents the relationship between soul and supreme soul (Atma & Paramatma). It also invokes blessings by God so that the one who ties it, always does Good Deeds.