nail down (someone or something)
to make certain or sure of something
I am trying to nail down the exact time that the meeting will begin.
Mountains in India
Guru Shikhar, a peak in the Arbuda Mountains of Rajasthan, is the highest point of the Aravalli Range. It rises to an altitude of 5,676 feet (1722 meters).It is 15 km from Mount Abu and a road from there leads almost to the top of the mountain. A cave at the summit contains a temple of Dattatreya, an incarnation of Lord Vishnu. Adjacent to the temple is the Mt Abu Observatory operated by the Physical Research Laboratory. This observatory hosts a 1.2m infrared telescope and also several Astronomy experiments.