Tilaka refers to the markings which are applied by the devotees on their bodies. This reminds the devotee that he and everyone is the eternal servant of Lord Sri Krishna. By wearing tilak not only does one identify one’s body as the temple of the Lord but one is also blessed by the auspicious protection of the Lord. The mark having a U- shape represents the lotus feet of Lord Vishnu, and the oval part represents the leaf of Tulasi Maharani. Tilaka is applied with the recitation of the names of the Lord. We apply tilak on twelve parts of the body, and the twelve names of the Lord are recited with each application.
“In Kali-yuga one can hardly acquire gold or jewelled ornaments, but the twelve tilaka marks on the body are sufficient as auspicious decorations to purify the body. “ SB 4.12.28 Purport
“I have no objection if members of the Society dress like nice American gentlemen; but in all circumstances a devotee cannot avoid tilaka, flag on head (shikha) and (tulasi) beads on the neck. These are the essential features of a Vaisnava." (SPL to Brahmananda, 14th October, 1967)