Vaishnava Tilaka

What is the reason to put tilakam? And why devotees in ISKCON put it so long till the nose? I am working in office so how can I apply it?

Tilak is a traditional mark to identify devotees of Krishna. It is made with a sacred clay from a holy place in India. It is worn to remind the wearer and everyone else that, the body is a temple and within the body resides the individual soul and the Supreme Soul, Krishna.

The ‘U’ represents the Lotus feet of lord Krishna. The mark below represents Tulasi leaf. This is the beautiful ancient Gaudiya Vaisnava tradition and an ornament of a devotee. If one cannot put a tilak due to circumstances one can use water and chant the mantra. This should do.