When the middle finger and the ring finger press against the thumb, while the other fingers are held straight we get the Simhamukha Hasta. Simhamukha means Lion -faced. In the Hindu Mythology Lord Narashimha Murthy (an incarnation of Vishnu) has the face of a Lion. He is Known as the “Great Protector” of his Devotees .
Lets take a look at the viniyoga shloka (uses)
homay shasho gajare darbhachalane padmadamani
simhanane vaidyapake shodhane samprayujyate
The shloka says that this hasta can be used to denote :
A Fire Sacrifice (Homa or Havan)
Movement of darbha grass. This grass is used by the pujari to make rings and worn during the time of pooja to sprinkle holy water. It is regarded as sacred and is a must for all Hindu rituals. It is also called as Kusha or Munja.
Garland made of Lotus
Face of a Lion
Preparation of Medicine by physicians