The Mangala Charan (or "Aad Guray Nameh") is a mantra of protection that invokes the protective energy of the universe.  It should should be chanted 3 times in a row and is often evoked after the Adi Mantra ("Ong Namo Guru Dev Namo").  Many use this mantra to invoke extra protective energy around them.

Aad Guray Nameh
Jugaad Guray Nameh
Sat Guray Nameh
Siri Guru Dayvay Nameh

Meaning:

I bow to the Wisdom in the beginning.
I bow to the Wisdom through the Ages.
I bow to the True Wisdom.
I bow to the great, unseen Wisdom.

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