Each Yantra has a separate and distinct purpose. Some yantras are
worshipped in temples, some by individuals at home and some are worn on
the body (usually of triangular or rectangular shape) either around the
neck, the arms, or kept close to the body in another location.According to how the yantras are used, they are classified into seven divisions :
Sharir Yantra
There are seven chakras in the body through which Kundalini is awakened. There are seven Yantras for each chakra and the Yantras are worn or used accordingly. Since, the Yantras affect a particular part of the body, they are called Sharir Yantras.
Dharan Yantra
These Yantras are worn on the body for specific reasons.
Asana Yantra
Asana Yantra are kept under the "Asana" (mat) during Sadhana (meditation). These Yantras are also kept in temples, in foundation of buildings and houses.
Mandala Yantra
The Sadhakas (Sages or saints) sit in the shape of the Yantra. Nine people participate in this ritual. One sits in the center, four persons in four directions and others recite other mantras.
Pooja Yantra
These yantras are installed, whether in temples or homes of individuals, while pooja is taking place. They may be for different religious deity worship, or for the different planets in our solar system.
Chhatar Yantra
These yantras are not placed upon the body, but kept in the pocket, or under a turban (or hat).
Darshan Yantra
These Yantras, if seen, blesses the Sadhaka or the one who sees them. They also purify and bless the place they are installed in. The examples of such places are temple of Jagannath Puri where the Ishairon Yantra and in Shrinath Dwara where Sudarshan Yantra is installed.